Can I use any Ni-MH AAA for my cordless phone?

[RAMd®d]

You'd just want to check the capacity of the cells/batteries to be sure the replacement batteries will power the phone for as long as the original sets did. If the original batteries were say- 1000mAh, you wouldn't really want to replace them with ones that have a 800mAh rating. No harm, just shorter talk and standby time.

And the more frequently the batteries are run down, the shorter the over all life span.