I've had the same problem, since I set my new iPhone 15 up on the 26.9.23... I've made numerous calls to 150 & received numerous calls back. Keep getting the same response, that the 'service order has completed with an error'.
I was told the problem was only with iPhone 15. That's obviously not the case, after reading the post on here & I've tried putting my sim back into my old phone & it's the same, I still can't access my voicemail.
It's not very helpful as I work in a Castle, with 4ft walls in some parts & 9ft thick in others. I also have an 85 year old mother, who is frail & I am her main carer. I was looking to leave EE but as I have just signed up for new contracts, it's going to cost me over £1,000 to leave... 😞
I have now resorted to sending a letter of complaint into the Customer Service Department, but I am very doubtful I will hear anything.
My next call back has been arranged for 4pm on the 17.10.23 but I have no faith it will be sorted by then, as the whole sage has gone on far too long.
The only positive in all of this I have been talking to someone called Martin who has been great throughout & at least he calls me back when he says he will.
If I have any update, I will put a post on here.
