DO NOT contact QDR. They are acting solely as a debt collector. All debt collectors are powerless to do anything and should be ignored. We do not need to know about any debt collector correspondence you receive and you can safely ignore it.
Thi sis going to end up as a claim. I doubt QDR will be involved. It is most likely going to be passed to DCB Legal who will issue a Letter of Claim (LoC). Whoever, issues the LoC, it should be responded to. Let us know when you receive one. A real LoC will give you 30 days to pay. Anything giving you only 14 days, even if it purports to be an LoC, can be safely ignored.
Eventually, a claim will arrive. We will give you the necessary advice on how to respond. The most likely outcome will be an eventual discontinuation. No one who is receiving advice on here pays a penny to ECP.
So, when you receive a real LoC, show us and we will advise further. Continue to ignore anything else.