They have an option on their exchange where you can create orders for fixed rates. At what every price you create the order the exchange will be carried out at that rate itself. Actually they provide two options to users:
- Once is the exchange will be carried as per the market rate
- The other is fixed rate where the order is executed at the rates you create the order
It is more easy to understand when you actually visit their exchange page. I have used it so I am felling that I have explain you well. Here I am sharing the link you can check out both fixed rate and the other:
https://coinswitch.co/app/exchange?from=btc&to=eth