Is there a free transfer service to and from the airport?
Unfortunately the free transfer service to the airport is not available
No, there is a service but it is not free. The Hotel Concierge will arrange a taxi for you at your specified time. Cost is DH100 and they provide you with a voucher for the taxi, assist you with loading your luggage and generally make it very easy. There is also an airport shuttle which runs regularly and is at only DH5, but you would need to take a taxi to the bus terminus.
Get an answer from Cassells Hotel Apartments staff and past guests.