Demanding payment but don't want to provide statement

I owe MTN so my account go handed over to MBD INC for collection. I went to the branch to see the statement to verify the amount and they mentioned they don't have access since the account is handed over. I called MBD INC and asked for the statement a month and a half ago and they said I'll get it in seven days. During the seven days they still called and sent messages demanding the payment and I told them I can't pay until I see the statement. It's a month and a half later and still no statement??? But they continue to harass me for payment without the statement. I've called them around six times including yesterday with no luck. Wondering if this is a strategy so I don't pay!!!