Patrick J.
Please give us more info.We are giving comments without a full picture ,let us know lender/collector etc, we probably know their way of operating.
From experience ,this looks like a debt collection company trawling to see what they can get from old debts that they have bought.
Since you have paid them something, then you are a likely candidate to pay them more and are a (soft) touch to squeeze.
1. Do not answer any Withheld numbers.
2. If you answer a call from them , do not give your date of birth to the caller, remember they are ringing you so its up to them to ID themselves (probably they will not do so as it puts them in probable breech of data protection)
3. Request copy documents and statements.Do a SAR (subject access request )to whoever last wrote to you.
4. Request no further contact until you have sighted said docs/statements.
5. Keep copies/notes etc of any future contact .
Don,t use Garda/Ombudsmans time on this.
Unless and until you have sight of a proven genuine debt ie Docs/statements ,do nothing.
I do not expect you to get clear documentation , so expect this to die off in time.