How to change CSC code with an sony E4g ?

[AC Question]

Hello there,

I bought my phone in England and I unlock it in order to put any SIM card in.
I moved to Spain last week and I got a SIM card from Movistar. However, when I text Spanish numbers my phone adds the country code automatically which I do not need.

Is someone know what I should do to change my CSC ?

Many, many, many thanks,

Jennie