Do you have to cancel for that?
My guess is yeah you would as it's for "new customers only" which may or may not work if they class you as a returning customer.
My deal might not be the best but it should be a guideline on what you can be offered if you hold out.
My usage might reflect the reason for them not wanting to provide a faster speed.
I can't say I download much but when I can just delete and reinstall my steam games etc it might not be great for them!