Thank you for your question.Is the app still downloaded on the same device and was never deleted - if so deleting it can erased data and this might solve the problem.You can also try logging in with your email address and try changing the phone numbe...
Please contact support and they can help you as you cant do it on your own without the app They can be contacted here https://www.publicmobile.ca/en/on/send-usHave a good weekend