Yes, it is possible to have a Swiss number and make a forward to the Spanish mobile number. The forwarding can be made from the PBS interface received during the activation of the service. When you use a Swiss number, it's like you're in Switzerland. The people who will call you will not know that your call is being diverted to another number and will not know that you are physically in Spain.

You will pay every call forwarded to your Spanish mobile. To avoid the costs of forwarding, you can also receive calls on your mobile phone, installing an application (zoiper, media5fone, GS wave ...). In this case, you can make and receive calls with your Swiss number and only outgoing calls will be charged. Incoming calls are free. For this your mobile must be connected to the internet to receive calls.