We rent a small unit on a building. AT&T came to turn on phone for us, however, they only do outside. Later, we came to the unit, the phone has no dial tone.

Would you please tell us what to do to get the dial tone? Thank you very much in advance.
Thu.

I would start at their box outside, open up jacks inside. The wires on their 2 terminals need to connect to the red and green on phone jacks, wires used most for line 1 is red and green, or white/blue and blue/white.
If part of a building, your wiring may go through other units, or other units may go through
Your jacks. Tone generator and telephone test set is best for this.
You may run a cord from your jack to outside with phone attached, when you have dial tone, you are on a pair, or cordless phone, may not be your pair.
Call your number to be sure.