if you use synthetic oil can you change back to using regular oil next time? on 2010 Buick LaCrosse

I always use synthetic oil when I get my oil change but when left at the dealer for some repairs they put in regular oil by mistake and said you can do this with no problem to the car. I s this true or should I go back to them and get it fixed?

Asked by for the 2010 Buick LaCrosse
You can switch from one to the other with no problems as long as they used the same viscosity.