Debited for a gadget that never worked

I was recently called by mtn call center agent, I was offered a wifi. The agent did confirm that there is network coverage.

The device did arrive, but it was not working, I tried to reach assistance. I could not via the phone, so I wrote them countless emails. Almost the entire month. I decided to return it back to mtn. I did return it and I was given a.reference number (IRMS ***.). To my surprise I was debited for something that never worked and it was returned. I tried to dispute the.debit order but I was not successful. This is irritating because I never used the gadget. I feel i was sold a dream that never materialized. They must return my.money, end of the.story.