mondo mobile worse

Hi.im Robert i had a data rooter with mondo mobile and MTN. They phone me and courier me the rooter which i enjoy for 3month .after that i experience a network problem. i call them and they told me the tower is vandalized .we agreed that they are not going to debit for those month. At the end of the month debit run. i call them to enquire they promise to refund the money. The following month they debit again,when calling them to enquire they told me to find the refund on the technical support .i told them i did not know about those guys they told me there is nothing they can do. I disconnect the rooter and now they send me to dept collector , they are calling me every minutes will you pleas help