We used the online booking tool Calendly to allow refugees to book appointments for some of our services.
We used the free account of Calendly.
This works very well when you have pre-arranged time slots that you want people to book e.g. 30 minute conversations.
You cannot change the labels and language used in Calendly. For some of our users this was a barrier and so we eventually decided to build our own version of Calendly using a lot of the workflows you would find there. This gave us the ability to use labels and language that worked better for our user groups.