Why could i get messages from twitter but not send them in

I have been fine with twitter for a while, but all of a sudden i encountered some glitches... I was unable to text to twitter, which meant no updating or turning it off. i tried to delete and start over but now it won't send in my verification code. I already tried contacting twitter and they said go to my cell phone carrier, so i did. I asked them and they don't know anything, so they say it's twitter. Has anyone else encountered this and how do i fix it?