Upgrade handset still not received

I ordered an upgrade on 18th November. I received an email stating to expect my new handset to be sent out 48 hours. By 30th November I still hadn’t received it. I was told that they did not have any in stock and would not be getting any in until 21st December. I aid that I was not happy they had offered a contract that they knew they didn’t handsets for and they offered me £10 off my next bill by way of compensation. I still hadn’t received it and contact them again around 30th December. I was told that someone would get back to me in 48 hours. No one did and on 2nd January I made a further complaint. I was told that someone would respond to my complaint within 7 days. I then got an email asking me to phone the complaints number. On 8th January I spent 50 minutes on hold to the complaints number before I gave up. I contacted live chat and they said someone would get back to me within 24 hours - they didn’t. I contacted live chat again the following day and was told someone had rung me - they hadn’t. They again told me that someone would contact me within 24 hours. I said I wasn’t confident they would and asked for a deadlock letter so I could refer matters to the communications ombudsman. They ignored this and said someone would get back to me within 24 hours - they haven’t. I can’t refer to the communications ombudsman until 8 weeks after my initial complaint on 30th November. Is there anything else I can do in the meantime to try and resolve matters as I feel I have exhausted all options. I need the phone, so I can pass my old handset to my daughter, who has broke hers and needs it for travelling to school.