Hey there heyimlaila
Thanks for using QandA platform
So the phone number validation issue encountered during the Azure Subscription Sign-up process can be fixed by opening a support ticket and connecting with the Azure subscription team.
So I suggest you to use one of the contact numbers from the link below and create a support ticket. - https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
The subscription team will get on and help you to resolve this,
reference - https://learn.microsoft.com/en-us/answers/questions/1431080/we-re-unable-to-validate-your-phone-number
Kindlay accepts the answer if this helps thanks much..