My ifone isstuck on sim not valid mode

I have the same reoccurring with my charging cable. It tells me that the device may not be supported because of the cable. I simply pull it out and put it back in until it works. Happens on my car stereo too when I listen to music via the Iphone6.

Try turning off the phone and removing the card and cleaning it with a dry 'CLEAN' cloth and place it back in with care .Finger prints or body oil may be effecting the card.

Don't use any solvents or water, not even a damp cloth!

Sometimes just turning off the phone and turning it on again helps.

Hope this helps

The message "SIM not valid" usually means that the phone is locked to a carrier which is NOT the same as the SIM in the phone.

You need to talk to the carrier to which the phone is locked. Ask them if you qualify for unlocking. Only the carrier can authorise the unlock.

Where exactly did you buy the iPhone 6 ? from MTC ?

Where in the UK did you buy the phone from? Did you buy it directly from an Apple store in the UK? If you did, then the phone should be unlocked.

If you did not buy it directly from an Apple store in the UK, then there is a strong possibility that the phone will be carrier locked and in this case, you will need to contact the carrier to get the phone unlocked. There is no other way to do this and nobody else can help you - only the carrier to which the phone is locked.