Terrible service

Saturday I booked my blackberry in at Cresta (it keeps rebooting and I can't use it at all. Anyway, I went back on Sunday and the girl Danelle there refused to phone the workshop because we got the sms to collect before 2 and when I went there it was 1:40 and she refused to help us. I then went back on Tuesday and picked the phone up but they had done absolutely nothing on the device except for a software upgrade which they did a month ago already. The problem isn't fixed and I still can't use the phone. When I went the previous time, I asked the guy Vincent to please book it in and order the parts and whenever I go back they give excuses, up until this weekend when they didn't actually fix it.