Returns - call center not answering calls and no feedback from email to customer services

I took out a contract for a router with data so that my kids can also have access to data on their tables when we aren't using the wifi at home. When I received the package I was told by my husband that we already have such a router so I need to return the package as well as cancel the contract. I have tried phoning Vodacom (because my billing comes from them) only to be told that I need to contact Mondo. I have tried for 3 consecutive days now to try and get hold of them but with no luck, their call center line is apparently experiencing high call volumes so you can't get through and then they tell you to email them and yet no response either. I don't want the contract with them, I want it canceled and they must come and collect it asap. Anyway, if you already get such poor service at the beginning of a contract just imagine how bad it will get later on