Send back before problem where resolved

I experienced some signal problems with my iPhone,some time I lose my singal both 3 G and 4 G I decided to take my phone in to the branch for repairs,after explaining the problem they send my phone in for repairs, after a few days they phoned me and told me that my phone only needed a software update....I continuesly told the that that was not the problem but they just send my phone back for collection....I collected the phone and the problem is the same and not resolved...I have my own business and use my phone for business purposes...now my phone is continously not working I can't phone and costumers can't reach me so I am losing business as we speak...I feel this is very poor costumer service...I could have just done my software update at home