Cipher. So many ways to approach that one. You could make a dump with your phone number backwards and then make a bet that you will reveal their phone number. Go through the basic star sign routine, once the try dialing the backwards number, say “hold on, lock your phone so it’s fair. You Taurus folk are so backwards” and then ask for and unlock their phone and make up some excuse for it being backwards and put the numbers in one by one and hit dial. Show their number on the screen of your phone as it rings out.
You could also simplify it and make it seem like a numbers trick. Take and multiply your area code by the first 3 digits divided by the last 4 and then peek it. Play it off as a mentalist thing. Or if you already have a routine go through that once you got the peek.
Lot of different ways you could use that tool. Those were just a few off the cuff ideas.