Yeah - it's a problem with the site at the moment as far as I can see and it's hitting several operations that would normally work. If you have enough cash credit already then you can try buying the add-on (?) by text:
How do I buy stuff by text?
If you need to contact support then since the online form mentioned here
How to get help
seems to be problematic for some or all users right now you should try the email address:
support@48months.zendesk.com
Hope this helps.
