How can I fix stuck data transfer on my new iPhone?

I have recently upgraded to the iPhone 15, whilst attempting to transfer data from my iPhone 12 i have encountered multiple issues, firstly with the software update being stuck on the spinning icon after clicking “Update Now” after downloading the update, i got past this by restarting my iPhone.

However now i am stuck on the screen which says “transferring Data from iPhone” with a time estimation on it. The time remaining has been stuck on “estimating….” For several hours now, i started the transfer from this screen when i left for work and when i returned from work hoping it to be completed, it was still stuck on time estimating with nothing of the Bar completed.

I have contacted Sky who is the network i am with and they have been nothing but useless, they even sent me a different phone as they believed it was malfunctioning however i am having the exact same problem with my knew phone.

If anyone knows how i can sort this issue out please let me know as it has been 3 days now of attempting to transfer the data and i am starting to think i should give up and start from scratch with a new Apple ID but I don’t want to do this.

Please let me know as i am starting to become quite frustrated with my lack of progress and i need my phone for work

Thankyou for taking your time to read through my problem, any help would be appreciated

[Re-Titled by Moderator]