What are the problems with outsourcing the processing of the client base?

Question

Outsourcing

We want to try to freelance the initial processing of the client base.
It is supposed to use our virtual telephony, the contractor works through the sip account provided to him, we pay for calls, it is possible to transfer to a technical specialist if necessary, conversations are recorded.
The results of the call are recorded in a table. There is a call script. Number of initial counterparties ~200-300.
Who has tried this? What problems can there be and what to look for when choosing a contractor?