receiving less calls recently

i love Nokia C1-02, everything seems to work fine except now that the network is becoming crowded, i am not receiving all the calls i should be, and i am not able to call out like i used to. i might be getting half the connections i used to get. Other phones, especially older, simpler phones in my home do not have this problem. i have tried a few other phones, but i don't like them. I want this one to work. Can the incoming and outgoing strength be boosted on this, by either myself or a professional? Thank you.