CellPhone Problem

Good Day<br> <br> on the 05815I went to Exact to purchase a cell phone (Z3 Blackberry)and I was told by the salesperson that should I encounter a problem with the phone I must return it to the store, I bought airtime to load it on the cell phone within an hour there was no airtime in the phone, I was then advised by a friend to switch off data on the network settings, but then I realised after deactivating data I cannot make calls, this is not the only problem I am encountering with the phone, the phone is not user friendly, takes long to even open applications, when you tilt it the information is not displaying accordingly, I went to the store after 2 days of the purchase to return the phone, when I complained about the problem they showed me the contract I signed which during the purchase they did not show me the contract, and on the contract I noticed that the device was supposed to be tested, but that did not happen, I was made to explain this problem of the phone countless times and while I was explain one of the sale person was laughing at me, so I do not know whether maybe I am stupid by not being able to address the problem in a technological way of their standard or what.