You can delete the service from the services homepage by clicking on the cross next to the service.
Setup > Services
It is recommended that you de-activate the service instead of deleting as this will allow you to reinstate it again in the future if needed.
Alternatively, if you wish to stop offering a service, you can also change the offer end date to the date you wish to stop the service from.
You can do this by going into the edit section of the service.