Samsung S6 Edge problems

Pre-ordered my Samsung S6 Edge and received it on the 10th April 2015. For the first month the phone was working wonderful and super fast. Then i experienced that people cannot get hold of me,i will receive a missed call message. When speaking to people the phone will just cut-off. Sending messages and Whatsapp messages were impossible and would not go through at all. The phone did not go on 4G and became very slow, one could not go on facebook it would just not download. I took it in to Alberton repair centre and received it back after 7 working days with the message that the \software updated"job #***2. After receiving the phone"