renault senic 1..6 always a problem never the answer!!?

i have had the vcar for 8months now i have had coils changed to times!! everytime they go i get a warning saying check gear box the electric fault then i get it plugged up tathe machine and it comes up coil!! this is the third time it has happened is there a prob with the gear box?? or am i just paying back allley garages when i shud pay full price and get it done properly! please help!!!!!!!!!!!!!!!!!!1