Rochester handed over the account without communication

I have just contacted the company a after receiving a phonecall from a different company claiming to have taken over my account.

My account was handed over to another company which I last made a payment in November and I'm yet to pay today or tomorrow, however I was just informed by the new company who's name I couldn't even get that this account was handed over in December.

I would like clarity and at this point I emailed the store and was advised the account is with another company therefore I need to contact the company directly.

All I want to know why was I not informed that the account has been handed over to another company , what if I would have paid as per normal. Can I rather pay the store directly just to pay off this account.