For the last several weeks I have been running into this error when trying to change my plan from Self Serve. I was finally able to change my plan by NOT choosing a perk, but I would still like to have the option to choose one (rollover data, premium voicemail, etc.) , given that it has been offered to me.
I have tried using different devices and using a private browser, which made no difference.
The last error code I received: Transaction ID here: U1730164434461I67081