Most disappointed with response after many endeavours to return mobike wifi unit

In January 2017 I received a call from Vodacom telesales marketer regarding mobile wifi. I ageed to try the unit but made it very clear that we dont have cellphone coverage on the farm . The lady assured me as well as her supervisor( who I insisted to ask) that the unit will work but if it does not I can just return it. I called within the 14 day trial period to advise the it does not work. A return was logged. Nothing happened. I called again a month or two later.....again they will arrange for collection. And so it carried on. I took it to two Vodashops to return myself.....cannot accept it, Vodacom must collect. They very easily found the place to deliver, now they cannot collect. I receive references all the time but that is all!!! I am still paying every month for the unit. Last time I spoke to them they said I must pay cancellation fee because there is still one year left on the contract! I now really dont know what to do. My last call was on Friday 2/2/18 . Still waiting to arrange collection. Because we have no cellphone reception I gave alternate no for them to arrange collection. Also no call received yet!!! The telesales are so eager to sell no matter what!!! I would have loved to keep the unit if it worked, but now I am stuck in a contract, paying and am unable to use. I have been a customer for approx 20 years!!