There are many such services, but most are scammers. However, I'm going to outline a few basic steps to help you locate, verify, and deal with any exchange service without falling victim.
First off, if you are okay dealing on P2P exchange platforms, then airtm, Binance, etc. are reliable ways to cash your Bitcoin. However, if you prefer to deal with individuals to boycott delays and fees, then BHW is a great forum to find reliable partners. Deal with members who have a high status or at least Jr. VIP preferably sellers. Communicate with them through BHW internal messaging service only so you can have proof is something goes wrong. Transactions will be swift, communications documented, and fees lower.