scam. don't do anything.

Zelle has its clawback feature, if it was an error, zelle will clawback the payment by itself. 

The scam was, the person will text you saying please manually pay him back the $700.  and once you paid him $700, he will initiate Zelle clawback feature and get the original $700 back.  

Just don't do anything.  Don't reply if someone text you about this $700.  They can call Zelle and fix it. 

Google zelle clawback scam.