Frustrated customer

My account was handed over to mbd and I've been getting so many harassment calls from so many consultants and on the 24th of April around 1h45 in the afternoon received a call from a gentlemen who was parking outsise said he was working for npnetwork collections on behalf of MBD and he had all the paperwork that showed all my information and he was there regarding truworths but now I've been calling mbd for more than three weeks no help they admitted to working with npnetwork but they still calling me to say my account is not being paid I don't know what to do now