You are correct. I was a SK3 user too with their plan. I was with them for more than 5 years. I hated TMobile largely due to their outages. Hope you called them to get reimbursed for that month. I got a free month whenever they had outages.I don't know about now but yes they did have a "Deaf" plan of data only years ago- I had it for about 5 or 6 years with my SideKick 3. I could have stayed with it but decided to add voice and get the "internet package" and a new phone as the SK3 was starting to crap out anyway. When I first got the SK3 I distinctly remember it was a plan marketed to the deaf with T-Mobile however I cannot remember if it was offered by some other group or through T-Mobile. I don't think I even have that paperwork anymore.
Have been with TMobile off and on since at least 2000... Still debating on switching (as eventually I will need a new phone...); Never had a problem with them service wise for the most part except the time there was a huge outage for at least a week.