ILR & alledged tax credit overpayment

Hi quick question please , when hubby first in Uk we claimed tax credits for a while as I only worked part time , as my salary increased and I went full time . I notified them and it stopped . Last year received a letter saying we still owed them quickly followed by letter from a debt collection agency , I contacted them disputing it , several letters later , and we've heard no more . We are due to apply for ILR soon and just wondered if the DWP still say we owe it would be a reason for HO to refuse . I've tried to ring them but been on hold 45 minutes and still noone to talk to .
Thanks very much

Call them again.

Every time I called HMRC, I got someone on the line within 5 minutes. They are polite and very helpful.

https://www.gov.uk/government/organisat ... -enquiries

Don't apply for anything before ensure that everything is sorted with them.