Unfair Customer Treatment

I'm very disappointed and disgusted by the service I am from RCS Game Store Account. For a couple of months I was unable to pay my account due to the repercussions of COVID19. Then finally I manage to get a job and started paying my account. So I received a call from MBD saying my account has been handed over to them, they offered me a settlement discount. I agreed to the settlement offer, paid off the account and they sent me a paid up letter and told me they are going to inform RCS to close the account as I requested. 2 months later I received a call from vvm debt collector informing me that my account has been handed over to them by RCS Game. I told the consultant that called me that I have paid the account and I sent them a paid up letter. But ever since I've been getting calls from vvm non stop saying I owe RCS. I don't understand why would they let their make commitments with the debt collection agencies and then once the account is settled, they send it to another debt collection agency. This is Unfair Consumer Treatment, worse part of it is that they don't even respond to the emails sent to them