what happens to my full-speed data when i change rate plans in the middle of my current paid service period?

Any Full-Speed Data you have already used will be counted towards the Full-Speed Data allowance of your new rate plan.

For example, if you change from a 2GB Full-Speed Data allowance rate plan to a 4GB Full-Speed Data allowance rate plan and you had used all 2GB already you will have an additional 2GB of Full-Speed Data to use before the end of your service period.

Conversely, if you change from a 4GB rate plan to a 2GB rate plan and you have already used more than 2GB of Full-Speed Data you will immediately be at the end of your allowance and receive Reduced-Speed Data.