To change companies

[kadioguy]

[From a TOEIC test]

---
Me: Why not "to change a company"?

Friend: "To change a company" woulnd mean "to introduce changes in an existing company"; "to change companies" means "to switch your place of work".
---
So, could I say "to change companies" is a fixed phrase in this kind of context, even if one only changed from one company to another?

 

[teechar]

Me: Why not "to change a company"?

Friend: "To change a company" would mean "to introduce changes in an existing company"; "to change companies" means "to switch your place of work".

Your friend is right.

So, could I say "to change companies" is a fixed phrase in this kind of context, even if one only changed from one company to another?

It's not a fixed phrase, but that (the underlined) is exactly what it means!
It's a formula:
change + plural noun.
e.g.
change jobs
change suppliers
change builders