the painter (not our client) is unclaimed with another number --- both biz have same address
OK I'm confused.
In original post you said "a small client has 2 businesses at same address" making it sound like it was ONE client with 2 different businesses.
Then you said "can we use the same cell number as he uses for painting"
Now you say painter is not your client. If diff businesses why on earth would the construction company want to use the painting company's cell?