Highly concerned

I had a contract with Mondo for an MTN sim card which had to be cancelled from inception and then reimbursed because they messed it up and charged me double for MONTHS. I never got reimbursed the full amount even though I sent all my bank statements through TWICE. And now more than I year later I'm receiving phonecalls from attorneys telling me MTN has handed my account over to them due to non payment. But my contract was with Mondo. The cancellation was handled by Mondo.

I tried phoning Mono today to try and sort this out but I'm unable to get through to a Mondo-MTN agent