How To Fix Mobile Phone Yourself >How To FIX Mobile Phone Signal.?

>How to FIX Mobile Phone signal.? - how to fix mobile phone yourself

I have a Sony Ericsson K550i (with the EDGE network) and the signal varies each time, when I returned to the WAP Internet. (Even if outdoors).
What can I do to keep it constant. I cleaned my SIM card with something, or a hotline to my service provider (to help me and how?) Or is there something else I do?