Hello Abdhullah Ariff,
Thanks for your question.
Could you try the workaround in a similar question here: https://learn.microsoft.com/en-us/answers/questions/1431273/we-re-unable-to-validate-your-phone-number
If you need to find the root cause of this though, I will recommend you create a billing ticket here: https://azure.microsoft.com/en-us/support/create-ticket
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola