Damage Cellphone

I bought a Cell C Atom dual sim at Pep Parow Centre. I got home the same day the second slot for simcard 2 did not work at all. Took the phone back, manager checked it out to see if it is the simcard. The phone was booked on. They gave me a different phone with the same value. I took the Stylo k1s, nine days after, my messages started getting full. Trying to delete old messages, phone just froze. I then took out the battery, switched it on again. The same thing happened. I called into the branch, a lady called Chantel told me, they must book it in for repairs and it will take a whole month and I cannot get another phone because my seven days is over. I mean it's not even two weeks yet. This is now the third phone I bought there that's faulty. Must I now really sit with a phone that cannot receive messages or without a phone for a month?!