Hi @doritos,
Welcome to TPG Community!
At the moment, there is no option to change the mobile phone number via My Account. Hence, you will need to contact our Mobile Support by phone at 13 14 23 options 2 and 3 and they are open during weekdays from 8AM - 7PM SYD, weekdays and public holidays from 9AM - 6PM SYD.
Let me know if you need further help.
Regards,
Angeli
