UNPROFESSIONAL and useless

MTN handed me over, but NuDebt's portal says I don't exist. They are ignoring my emails and failing to allocate my R650 payment. My balance should be R11,000, not R11,650." Ive sent them over 20 emails already and they do NOT respond. It's very frustrating and they are so unprofessional. They keep saying I owe them the full amount and aren't acknowledging my payment.