Again phone not working and replacement

Cell C did help me and replaced my damaged BB Z3 with a new one last week.<br> <br> Within a day or two the new phone had the same problem as the previous one, where once it looses network signal, it never finds it again until the phone is switched off or reset.<br> This is terrible for business and family as when they are trying to get hold off me, i have no signal and only find out if i try to make a call.<br> The major problem i am having is that I dont want a BB Z3 any longer. The store is saying they have to book the phone in, and if it is an out of box problem they will within a week give me a new phone.<br> I dont have a week as i have already lost a full month with the previous phone being in for repairs..<br> Please can CellC give me the same service like before and give me another phone, but not a BB please.