Refund from previous supplier

Do I need to contact my previous supplier for a refund on a switch or does bulb see to that. Avro energy owe me an overpayment I think

From previous experience you shouldn’t have to do anything although it can take a few weeks. If you dont get your credit after say 6 weeks I would phone Avro as they are responsible for your credit not Bulb, they will hold on to your monies until a final bill has been issued.