My iphone is not receiving calls

my iphone 3g 8gb has been acting up lately...i cant receive calls sometimes, like when i try calling myself it rings once and then goes to my voicemail...my iphone doesnt ring and it shows that i have all full bars, but when i take my simcard out and put it back in then i can receive calls again, but then a few hours later it starts all over again

i tried resetting the network settings but it just keeps doing the same thing over again

during the time i can receive txt messages and i can make calls no problem

I have a fix for this, i charge 30 USD to fix this..if you are in India then i charge Rs 1000, and the best part is that you dont have to send your phone to me, i will fix it remotely.