I’m a bit confused by your post. You say you think your pre service mileage was about 50,000 on a one year old car. This would be a phenomenal mileage, averaging about 1,000 miles per week, more than most sales reps would achieve.
Secondly, garages never reset mileage when servicing a car, unless your speedometer has failed and needed replacing.
I think you’re mistaken about your mileage and your true mileage is 17,000.