Hi, and welcome
Has the DCA bought the debt from UB or are they just acting as agents? If they have bought it the following advice applies to them. If not the CCA request should be sent to UB.
Send a CCA request to the DCA for a copy of the original executed credit agreement. You must send a PO/chq for £1 with this and a template letter can be found in this site's library. They have 12 working days from receipt of this letter to send the document otherwise they are in default and cannot pursue you further while that copy has not been sent.
After a further month, if they have still not complied they will have committed a criminal offence and could be fined or imprisoned.
This will at least give you some time to consider your options.
Let us know how you get on.
Regards, Pam