follow up texts after calls

Didn't know where to put this but here goes:

I wanna call tonight and other nights but I've been caught out before when I get texts afterwards and my gf finds out which causes alot of problems. Is there any way to opt out or stop the messages?

Can't use the landline either cos I've just moved back home

Use the long number, still works ok with a mobile and no texts back

nah dont think there is anyway especially if u use the short code as they chare u a connection fee what you could do is get a 2nd payg sim and hide that in the phone so when u wanna make a call then use that thus no texts and a happy u and happy gf