Im confused what’s a dca ? yes it’s on my credit file

I’ve been having an ongoing problem with British Gas for 2 years now about owing them money for gas which I do not. As I have no gas at my property due to everything been run off electric as I have a Mitsubishi eco fan system thing which generates underfloor heating, hot water etc. Ive had engineers come round to say I’ve got no gas yet despite this I still get bills letters etc. They said they think they may have found the problem that I’m receiving someone else’s bill from at a little street at the bottom of my road, and yet again despite this nothing more is getting done and I’m still receiving debt letters and also letters from a debt collection agency I’ve spent numerous of calls and my time on the phone trying to sort this and I always get fobbed off and told someone will look into it however two years down the line of stress, worry and fear that debt collection agency’s will turn up at my door seeking this money that I don’t owe it’s still not resolved and I just don’t know what more I can do and who I can go to for help? also could I claim compensation for all the stress and worry they’ve put me through