If they received a reading in July 2009 and didn't use it or investigate further, you might be able to get them to knock the first couple of months of your supply with them due to the billing code, or you may be able to get a good will discount if you complain hard enough. They will probably have made some mention on the bill that it is estimated. If you feel it doesn't make the consequences clear on your bills, this is the grounds to use to make a complaint - rather than let it escalate too far, they will likely offer some sort of discount. I wouldn't focus on their estimates being 'incorrect'. Ultimately they had very little information to base these on (you are a brand new customer to them) and they have attempted to read the meter (their word, of course), they're unlikely to budge on this. That said, Npower will be able to pursue you for most of the balance. You share the responsibility as a consumer to ensure accurate billing by checking your own meter. If the readings are now accurate, and the start reading they used on the account matches the final reading from your previous supplier, your bill would stand (the options in my first paragraph excepted) as you've used the energy in question.

What Surfer and Siany say isn't quite correct. The important reference number for gas is known as an MPRN, sometimes just MPR. MPAN refers solely to electricity. What you need to ascertain is who the registered supplier is for the MPRN for your flat. Exactly how you do this can differ depending on a couple of things. Initially, check to see if the MPRN is printed on your meter/pipe, or on a tag on the pipe into your flat. This is very rare, but if it is, that's the MPRN you should be billed on. Find out who the registered supplier is, and see below for next steps. Firstly, contact UW. Ask them what MPRN they are billing you on. Hopefully it will be an MPRN shipped by National Grid (formerly Transco) and not an IGT, as that would make things more time consuming. If you trust UW, ask them to check a national database called Exoserv for you, and tell you what address is down on there for the MPRN. If this address matches your actual address, UW are your rightful supplier. You can check this yourself by calling National Grid, 0870 608 1524. If you are shipped by an IGT, see this page for more info and telephone numbers on who to call. If the address on Exoserv/with NG/with the IGT's records doesn't match your actuall address, find out if there is an MPRN logged under your actual address. If there is, find out who supplies it. They are your rightful supplier; contact them and explain the situation. Under the spirit of the billing code, they shouldn't back-bill you for more than you've paid to UW, but I make no promises. It is entirely possible there is no MPRN which is logged on a national, industry-wide database as matching your address. Sometimes they'll be logged as Flat A, B, C when it should be 1, 2, 3 etc. This makes the situation more difficult. If you are in this situation, there are a lot of variables that determine how to proceed. These bad boys can get messy. If UW do turn out to be your rightful supplier on the original MPRN, they can correct their bills based on the correct MSN/reads, as it's within one year. That said, ensure you know where their reads have come from and don't stand for ridiculous estimates. Good luck.

Some companies will charge to do this, or require a deposit. Some will do it free of charge. Call and ask them, and if you decide to go with one company that will do it free of charge, take the full name and extension number of the person that advised you it's free, and make a note of the time of the call. Once you've switched, use this person as a point of contact (unless they're in a sales department and unable to arrange meter exchanges, for example), and be certain to complain if the company changes their mind later and won't do it for free.

Unfortunately the electricity situation for you isn't brilliant. Whilst you have been misinformed by your letting agent regarding the electricity supplier, it remains your responsibility as the person responsible for the electricity to find and pay the correct supplier (especially since nPower themselve advised you they're not the supplier, and BG have been sending you bills). They are unlikely to accept monthly payments, though you can certainly attempt to negotiate and explain the situation. The likelihood is that you'll need to get a prepayment meter installed with the debt loaded, or they'll do this on warrant (which, after 10 months of non-payment, they will get). The gas is a seperate issue. I would recommend finding out if the MSN you've been paying nPower for is for your flat. If it is, speak to nPower and find out if they're still registered as the supplier. If not, and British Gas have indeed taken over your meter without permission, advise them you'd like them to treat it as an erroneous transfer. It may be that BG have supplied your gas all along as well and nPower have been billing you in error, but one or both of the companies should be able to help you investigate this.

An energy company needs to splash out £600 every time a complaint reaches ombudsman stage, so even if the ombudsman might be likely to rule in their favour, most will avoid it for bills that aren't significantly higher than this amount, as once man hours are added in, it becomes more economical to write off balances.

The first thing you need to do is ensure you are being billed on the right meter. There is an easy, quick 100% reliable test you can do yourself. Switch off all gas in your property. Check the meters. If only one of them is not moving, it is probably yours. Return to your property and switch on several gas appliances, return to the meters and check to see which meter has started moving. Repeat if you wish. The meter that responds is the meter that is yours. Ensure this is the meter you're being billed on, and ask your supplier where they got their readings from for this meter. The thing to bear in mind is that the meters may be logged incorrectly on the national records for gas, and may have been for years. This is an extremely common problem with gas meters in flats. These mix-ups can be difficult and complicated to resolve, but ascertaining your correct MSN is the first step.