Bad network coverage

Hi, <br> I got a new sony xperia c3 On my cellc upgrade..99% of the day i have absolutely no cellphone network, but the bars are full! People phone me and they always get voicemail. I had to get internet at home to use whatsapp and to surf the net. Atleast then ppl can get hold of me via whatsapp. This is a problem when im at work and ppl cant get hold of me. I pay alot of money each month. The reception is so bad since end of last year... What can one do about this? <br> This sucks very much. Paying and not at all getting your money's worth.... Your logo should be \c for yourself how **** our network coverage is". im a very digusted client!"""