While the meaning of your opening sentence can be understood, "unregistered" really isn't a word. Perhaps you can say:
I am writing to request that my registration at Varsity College be withdrawn.
where I come from
As a rule, you shouldn't end a sentence with a preposition. Maybe change it to read, "Madagascar, my homeland."
For a closing paragraph, it's always a good idea to end with something like:
I appreciate your assistance in this matter. If you have any questions, please do not hesitate to contact me.
Of course, you include your contact information (phone number, cellular phone number, email address, etc) in your letter.
- For Teachers