I'm sorry that you're having trouble with texting. Your post title says USA, but you mentioned you're in the UK currently. Can you clarify this for me?
If you're abroad, you should check your roaming settings in your online account here in the Plan and Devices setting. If this is off, you will need to enable this but there is no guarantee that this will work now you're abroad.
If you're in the UK, I would advise giving us a call on 789 or 0345 6000 789 and we'll look into everything.