Can my unit make me change my MOS?

I'd need more info before I can chime in. Are you active, guard, or reserve?
What kind of unit are you in? This may be important because if you're in a certain unit they may not have or may be losing slots for your MOS.
Ultimately I haven't seen forced reclasses in a while. Usually it's when an entire MOS is going away. Let me ask around though. SFC (Join to see) is someone on here who might be way more knowledgeable than I am though.

Unfortunately this happens often in reserve units. Large scale reorganizations seem to occur every five to six years. You could contact your Unit Administrator and inquire if there are any openings in nearby units with your MOS, but it is unlikely there will be. I suggest you take a look at what positions are available under the new Modified Table of Organization and Equipment (MTOE or TOE) and choose a position that interests you and has leadership you are already familiar with.

Short answer, use this to grow your knowledge base and potential for college credits.

Gather around and listen to my tale of woe. I once was a 45K, Tank Turret mechanic/Armament Repairer we fixed all turret mechanisms and fire systems as well as all artillery and mortor. We were the sheet.
One day some TRADOC officer must have needed a OER bullet and the Army decided to break us up into separate MOS for each system. I resisted and ended up AN E5 sitting in an extinct slot for 6 years, fat and HAPPY.
Eventually I had to reclass to get promoted, and then again for E7. Now her i sm 57 yrs old sitting in an E8 slot waiting on a MLC (thanks COVID 19) to get what will be my last promotion possible because i will hit 60 and mandatory retirement. No chance for E9 Because I was HAPPY in my current MOS and stalled my career those 3 exact years I now need to retire as an E9.