Welcome to the community!
We are able to locate your account using your community details and we can see that there should be no charge if you change your plan to TPG-NBN service for additional 18 months contract.
We arranged one of our Account Specialists to contact you within the day using the contact number associated with your account. Let us know how it will go.
Based on the latest log, one of our Account Specialists tried to call you yesterday unfortunately no avail if you have time feel free to contact our Accounts Team 1300 993 011.