OP : What make is your phone?
Whilst I have been with VM, I have over the course of several years had continuing sporadic issues with Samsung mobile phones not connecting to wifi. No other makes or devices (tablets, laptops etc) are affected, just Samsung mobile phones. Sometimes just turning wifi off and back on, on the phone sorts the issue, sometimes I have to turn the hub off and re-start it.... but it's only ever Samsung mobiles that suffer from the issue