Other visa offices allow online payment of rprf but Accra doesn't accept it.
This info is decipherable from their website link with reference to their acceptable mode of payment receipt.
http://www.canadainternational.gc.ca/ghana/visas/fees-frais.aspx?lang=eng
If it is actually acceptable,the body language of medical request will show it.....I shared a friend's medical request mail from another visa office about 3 weeks ago in which applicants were directed to pay online which is not same with Accra.
Personally and professionally ,I will strictly advice you to follow the mode of payment on Accra visa office website link.
Cheers .