Hi,
Just thought I'd pass this on !

I bought a 'tarjeta' (pay as you go SIM card) from the Movistar shop for 25 euros. Of this sum, 19 euros was credit for the phone, so the SIM card cost 6 euros. I then went to the website https://www.canalcliente.movistar.es/ (it is in Spanish, so you need to know a bit or have your dictionary at the ready !)
and registered my number (enter your phone number & they send a text with your password) and then clicked on 'Consigue 6E de Saldo Gratis - queremos conocerte' (earn 6E of credit - we want to know you). This is an online survey (in Spanish) - you need to be able to give a landline number (I used a friend's), but apart from that it's pretty straightforward.

A couple of days later I checked my balance (saldo), and hey presto - it had gone up by 6 euros, so now my SIM card has cost me nothing & I have 25 euros of credit ! (You can get 3 euros back by filling in the form in your SIM card pack if you don't want to/ can't go online)

On the canalcliente site, you can also personalise your phone so that you recieve texts in English and get English if you phone the Call Centre; change your password; check your balance; activate your voicemail.....etc !!

Hope this will save someone some money !!

Cheers
Chris