Left 2 voicemails, knew my surname. Asked me to call back.
Both from a girl with a Belfast accent.

Rang the number from another phone, first a recording saying that the call would be recorded for quality and training. Then got put through to "Louise" in the collections dept. No company name ever given.

Update:

This number is the collections dept. for Ulster Bank.
The office is in Belfast.

Ulster bank to me it was certainly not them and that this was a scam