Cancellation and refund

I am so disappointed with your MTM, I bought a wireless router which did not have any signal and network, I called customer care where they advised for cancellation, I should go to any MTN store and cancel there, I went to MTN store today, they told me they do not cancel online purchases, they gave me a reference number and told me to call customer care to cancel

I called customer care, now they are telling me that I should go back to the store as they do not cancel month to month purchases, this is unacceptable, this one is telling me this and that one is telling me something else, very unprofessional of MTN, I just want my money back as that router still has the 100GB full, I did not utilise that data because of no signal