Whats link multiple msisdns mean

Hello, on March 2, I was re-directed to T-Mobile from Sprint. I was given the message that I could access my T-Mobile account within two hours. After completing this step, I stopped being able to receive text messages. I also noticed on the account history that the message "Link a MSISDN" appeared on March 2 - the same time I stopped being able to receive text messages. I only have one line. In the meantime, I purchased a new iPhone through T-Mobile. And I'm still experiencing the same issue with my texts. I can receive a few text messages, but not all. Any suggestions on how to "undo" the Link a MSISDN, to see if this corrects the issue?