Request of payment from OVO Energy for 2022 bill

I have just received an email from Past Due Credit Solutions requesting payment of an unpaid OVO Energy bill from 2022. From what I can see from previous email exchanges, we were originally with SSE (which then became OVO). The balance seems to be a migrated payment (from SSE) as we moved out of the property before the change from SSE to OVO happened. Looking back at my email exchanges, it seemed like I requested the final bill which was sent to me four months after moving out. I suspect this bill has gone unnoticed on my part as I'm not finding any evidence of payment.

Then, I received a new finalized bill from OVO in July 2026. If I really did forget to pay then I obviously don't mind paying. Nonetheless, I'm a little surprised about this popping up four years later and wanted to hear whether people have had similar experience.