Just activated my new 711 phone a couple of days ago
At one time I actually used this service as my personal full-time service, I liked it that much.
Punter, I don't think it matters where the texts are saved on a 711 "burner" phone, because neither the SIM card nor the phone is connected to your identity. No personal info or ID is involved, no bills, etc. You do have to activate your SIM card AND your airtime minutes. You can do these online from any computer.
To sign up for a 7-11 phone service (called "Speakout"), you simply buy the phone, airtime, and a SIM card at a 711 store. Once you've done that, you open the box with the phone in it, take out the phone and install the SIM card, and then dial a 3-digit number and follow some simple instructions to activate everything and find out what your phone number is.
I also prefer written communication, for all of the reasons Charlotte Edwards mentioned and then some. However you want to communicate, take advantage of burner phones now, before "big brother" starts clamping down on us
A couple of links:
Official Speakout page:
https://www.speakout7eleven.ca/
Unofficial page:
http://www.speakoutwireless.ca/