you could go about this a couple of ways. follow his/her guidelines or reschedule and/or make a request or 'path to switching from snri to ssri'

possible scenarios may include one, some or all of these: add PRN to ease withdraw symptoms when they are at their worst during the transition; slow down the rate at which to climb down on the snri dose; determine the amount of half lives you want to wait between stopping SNRI and starting SSRI (the more half lives that pass the less likely your going to have rare but possible complications ie SS). keep in mind patients with anxiety often mis identify relatively harmless side effects as being serious ones; don't use or greatly reduce the use of nicotine, alcohol, caffeine during transition

consider the cost/benefit ratio. zoloft is a pretty cheap drug even without insurance. it's under 10 usd with goodrx. are you currently in a stable economic position in your life? can you afford to reduce hours or miss work/school etc. try to find best time to do switch if you want to switch. personally i would switch if it were me. i have had better successes with ssri than snri