If you do not have access to a desktop or laptop, contact the customer support agents to have them swap the SIM card number for you.
To contact a Customer Support Agent, there are 2 methods:
Use the ticketing system for a faster response time. Click here and type Customer Support Agent, then select Contact Us, then select Other (or the topic that more closely matches your request). Click the result which states Click here to submit a ticket and follow the prompts, or,
Send a private message to the Customer Support Agent by clicking here You’ll need to be logged into your Community account for the link to work.
Watch for their response in your Community private mailbox which will be indicated by a number on the small envelope icon to the left of your Community avatar.