I used Emirates , flying out this week back in May. The Emirates free insurance was accepted for COE. My stamp runs out in March and I will be renewing then
pretty much everything in the UK is being blamed on the pandemic. It shouldn't be but that's their stock answer. I fear they will be using it for years to come. Had a government issue since last April and they are still using the pandemic for no available appointments.
I contacted them on Twitter and they got back to me in a few hours, gave them my number and they asked for the passport to verify and it was all sorted in a day
I called DTAC when I got back to the UK in April and they extended my number, it was 40bt for a year. Call your provider and they can ID you with your passport and you should be able to get your number on the new sim