Changed phone number to Singapore number

Hi, I am outside of UK and changed my phone number to Singapore phone number. I realized I couldnt update my phone number to the new one, as I couldnt find Singapore country code from the list.

I have tried to contact online chat multiple times, but the app stop responding when someone replies.

And on top of it, I am not able to find my UK sim card. Any suggestions?

Thanks!!

Are you able to use your UK number?
If yes- go to More > Profile > Personal data > Phone number
and just change it.