Cannot sign-up for unlimited data

I'm trying to sign-up for unlimited data. Every time I have tried, I get an error page saying it's temporarily unavailable. Error code DFPLN4000. Seems like this is a widespread problem, I guess the automated system to do this is broken or turned off.

We recently upgraded our plan to 1 Gbps and have been really close to the data cap numerous times. With IT work everyone at home, internet has become more of a necessity for us. We would like to remove the data cap before the end of the month.

Any help would be appreciated, thanks!