Cell C - shamelessly *****ing from me

So I took up a data contract with Cell C in mid April, received an LTE-A router and was supposed to get 100 gigs a month. On the 26th of April, the router suddenly stopped working. I assumed I had run out of my pro rata data so I just let it go. Come May, the router was still not connecting so I went to the branch where I had taken up the contract. I was told the LTE-A connection in the area where I live had been stopped so I cancelled the contract. Cell C debited my account for both April and May however, even though I had cancelled the contract, and the usage of their data was obviously zero due to the technical issues on their side. The branch again assured me that my contract had been canceled and that my application for a refund had been submitted. Guess what, those ******* debited my account again this month (June). So now I’ve paid for 200 gig that I never could use, and there’s no indication that this will ever stop for the foreseeable future. Complaining at the branch is pointless because they are just middle men. Calling Cell C is also not yielding any results. I feel like these ******* will continue *****ing from me for as long as they possibly can, and I know getting back my refund is going to be like pulling a tooth as I was already told I canceled the contract late, even though I couldn’t have known they had a technical issue, as there was never any communication from their side.