Looking on the internet deeply has found these results:

call them back to is the most popular phrase on the web.

call them back at 1322,000 results on the web	call them back to 1354,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Barbagli calls them back to order. Okay, just take a message, I'll call them back. If you'd like, I can call them back to break the Wizard. Just call them back and tell them I've got the perfect song. Call them back and tell them I need to know in 30 minutes. You can call them back and we'll get that order out. He promised to check us out further and call them back within ten minutes with an update. I'll call them back again to comfort me.

call them back at

1322,000 results on the web

call them back to

1354,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Barbagli calls them back to order.
Okay, just take a message, I'll call them back.
If you'd like, I can call them back to break the Wizard.
Just call them back and tell them I've got the perfect song.
Call them back and tell them I need to know in 30 minutes.
You can call them back and we'll get that order out.
He promised to check us out further and call them back within ten minutes with an update.
I'll call them back again to comfort me.