Upgrading existing NBN plan does not work through Account

[toriclutton]

Trying to upgrade my plan, but an error occurs every time. Error message below:

When contacting TPG, please quote this error code: < E:adsl_comm:thread_exists >

[RajenS]

log in to your account with below link 

https://www.tpg.com.au/home/myaccount

Under  NBN Account Management

select Change your Plan

click - I want to change my NBN plan and next 

now you can select your speed and VoIP plans 

also, I attached screenshots for you 

I hope this will help you