Wrong contract activated and devices delivered!

I app**** for a mobile contract online. It was approved and I received a phone call the same day from the call centre during which conversation we discussed the exact details of the MOBILE contract and specific phone. On the 28th I received a Wifi device and after enquiry was informed that a data contract was activated. I immediately informed them of their mistake. Until date they did not come to collect the wrong devices from me and apparently cannot cancel this wrong data contract as long as I am in possession of same. I called the call centre 3 times already and also went to the one store, but this issue has still not been resolved. I'm really fed up!