"unspent" and "spent" criminal offences was designed to give someone who has committed a minor offence the chance to avoid the problems that arise from having a criminal history. Spent are those that have been removed and unspent are those that are still on record.
Using my imagination here - if you disobeyed a court order to repay a debt, then I suppose that could become a criminal matter depending upon where you lived?
Having a couple of late mobile payments isn't going to show up on your PCC.