Text message

I have a friends cell phone number that since Ive gotten my  new Samsung galaxy phone when I text them it goes and comes back in the form of a text message.Before I got the new phone I had an Env touch and sometimes would send them messages from my  gmail account to their phone, but now I send text from my  phone to their number in my contacts and it may go and show their name but then it switches back to the email text.They are using at&t, which I have other friends that use at&t and I dont have this problem.Its bugging me ive even deleted their information and  put back in new and samething happens. Im thinking its google.