what do u mean u got study permit in mail? did u apply for study permit extension or in land application? r u still outside canada? if ur outside canada u dont get study permit in mail u get a letter of introduction. Once u produce that letter, visa and passport at the port of entry u will be issued a study permit. On that study permit it should be written can work off campus etc in that case u will not require another work permit to work 20hrs per week. So please clarify ur question properly.