The way it reads to me
You are currently using Att and billed via OTR a virtual 3rd party provider, who buys servicen in bulk
You will stay on Att and your cost of service will go up $20 unless you choose to switch service and your cost will go up $10
Or you can cancel service completely
It's obvious that Att has changed its agreement with OTR
Or that agreement included provisions that were not disclosed to customers,
But usually in the fine print, there is a statement about cost of service and blah blah changing at anytime