on air tv

I''ve received a call from a sales agent who misinterpreted themselves saying that she is calling on behalf of DSTV multichoice. she told me that I qualify for 2 explora and will pay fixed amount for 24 years.she confirmed all my detail which are believe they got them from multichoice.she told me that i will no longer pay my dstv installment as the amount will be converted into one account,To my surprise i was debited R160 from On air tv and also R509 from dstv multichoice. i've received 2 decoders and they told me they will sent someone for installation.can you please help me to cancel this contract and for these 2 decoders to be collected. i am loyal client for multi choice from 2006 to date and never skipped any payment