i was with T-mobile since 1994, never had any issues until i made the biggest mistake by changing to 4G . Since then never not once exempt maybe one or 2 times when we were outside London managed to call successfully my wife. Everytime i tried it says dropped calls. the same thing calling my son in Middlesex or my other son in Lincoln. I always simply either next or use whatsup. This is sad and i am 100% going to move to O2 next year. I tried all possible tips none worked.