@Peyman Panahi Thank you for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
By default, Customers are limited to purchasing one phone number per tenant for Azure Communication Services through the Phone Numbers SDK or through the Azure Portal.
If your existing ACS resource has a valid phone number and if you have deleted it then you won't be able to acquire the new telephone number immediately, you need to wait to repurchase until the end of the billing cycle as explained here.
To request a new phone number, you need to go through the Manual process (special order numbers) by following the steps mentioned here special order.
Feel free to reach back to me if you have any further questions on this.