Samsung Sghx700 — calls jumping

when ever i tried to make a call the call is going and the person on next side is receving, but can't able to hear anything, this is continuing for past one month, i have complained thrice to customer care no, they told it will b set rite.. but its noy so.. i face the problem in incoming calls also..
per day iam loosing nearly Rs10 like this.. its too hectic, if not able to make and recive calls then for what do v hv mobile.. its not happens with me, but for all the persons who use Airtel..that to only from last month, iam a student in ISM Dhanbad and here all my frds too hv the same prob's..
some time when i call chennai its going to bengal and alot of nonsense problem like this..
the complaint reg no[protected]. requesting u to o the needful thing..
being a stundents we hv our campus and telephonic interveiw if this prob's is going then really its worst.. so do the needful thing.