Very difficult to deal with mbd

My account for For Truworths was handed over to them and I settled the account but they keep on calling me everyday and different people and when I explain that I settled they being rude to me and they keep on giving me different e mails to send proof of payments but nothing is happening even those emails no one is responding but they calling everyday I even went to the shop with the receipts but they also can’t get hold of them as their phone always ring and no one is picking it up .

Another problem they keep on adding charges everyday as they say I did not settle my account where as I have proof of payments but this thing can’t be resolved the only thing that they are capable of is to dial my number without any solution.im really tired now of this thing please help