Dear Ms. Shierly,
re (John) Dakochan ID No. 1234
I am contacting you to confirm that I paid the International Student Semester Fee of $1234 Cdn. on March 14, 2008. I am looking forward to receiving the Letter of Acceptance. I would be grateful if you could confirm that payment has been received. Also, it would be most appreciated if you could please kindly e-mail me when you have sent the Letter of Acceptance. I am concerned in case there is a missed postal delivery.
Thanking you for your trouble.
Note: If you had written ...'that I have paid the International Student Semester Fee of $1234 Cdn.'
the present perfect tense would have been correct. However:
.you have given a definite date, it was paid on that date, it is done, over, as of that date, so use the past tense