As Prudie states, the international dialling code for Spain is +34, not +44 (which is the UK code).
So, if you've been given a number starting with +44, it's either an error or the person is using a phone registered to a UK network. (In which case you call that number from the UK, or from another mobile registered in the UK, in exactly the same way as normal, with NO international code at all. If you're calling from a Spanish landline you dial 00 44, in just the same way as you would if the person you were calling was still in the UK).