Antennas can only do so much. What they really do is semi-eliminate nulls when the phone is sitting on a table or on your belt.
As far as the Blackberry... Sorry about that. They have not only been going downhill the last several years because they can't keep up with iPhone and Android develipment, but the quality of the equipment and robustness of the OS are tanking as well. Its BY FAR the worst "smartphone I have ever seen. The ONLY reason I have one is that some idiot at the company signed a deal and we were forced to take them. Unless you HAVE to have a BB for work, consider something else.