Unable to maintian aircelgprs connectivity

Hello,Sir I am using aircelgprs on my pc with nokia 7610 using nokia pc suit 7.1.I used to loss my connectivity after a few minutes the modem activity staus shows connected&modem is sending&there is no reception.Then I haveto discnnect &connect frequently to get connected up.the speed is very slow how can i improve the speed .Iam using download manneger also.some times mobile shows G after disconnected by pc suit then i have to switch off the moble &switch on it to disconnect G in mobile. iam using data cable .Sir how can i over come these problems? is it better touse blue tooth?or i need to change my mobile then please suggest me a me some best suitable mobles.Is there any moble below Rs 5000/ is suitable?.i am having sc net speed booster also.