If no texting phone number is available from the User menu’s Phone Number (for texting) field,
sign into Plivo to confirm what phone numbers are assigned to the account.
If a phone number is no longer assigned, this is an indication that the account balance is depleted (or negative) and may require you to purchase a new phone number for texting. The account balance can be confirmed from the Plivo Dashboard:
The following article details how to prevent a $0 balance:
We recommend using the Auto Recharge Option to ensure that your account is recharged automatically when your credits drop below a certain amount to avoid an interruption in service.