Saw that my local store offered a better deal for less. I opted to change and was told I needed to replace my existing SIM card with a new 4G SIM. I have an old trusty iPhone 4 and this had a 3G SIM in until this point.
new SIM fitted and told it should be active within a few hours but to allow 24 hours. The phone displayed the ' no service' banner and then reverted to SIM invalid when I moved it to flight mode and back.
After 24 hours and no sign of a sync with the network, I went back to the store and the SIM WAS REPLACED. Guess what still no signal and the phone hasn't synced. I could understand if I had changed provider but come on. The online chat is never available and I haven't got a signal so can't ring the helpline.