Hi @Edenkim ,
Welcome to the community!
Thanks for raising this to us, we'd love to help arrange a call from one of our Mobile Specialists contact you to discuss details of account modification and plan change. Please shoot me a private message with your account details (Username/Customer ID together with the address on file).
I can log in, but I can not change my contact details, payment details, and password too. Even I can not change my mobile plan. How can I do now for it??!