What happens to the credit or debt from my old prepayment meter when I switch to PAYG?

I was with already with EDF when I changed to PAYG

Any credit or debt from your old prepayment meter will be transferred to your new Pay As You Go meter. This should take about four days. If you have an instalment plan on your old prepayment meter, we'll transfer this over too.

I've just switched to EDF from another supplier

We'll ask your old supplier to transfer your debt over to us (up to £500). If they agree, we'll take a small weekly payment from your meter towards paying off that debt when you switch.

You would need to ask your old supplier for a refund for any leftover credit (your balance starts at £0 when you switch to us).