I have unlimited texts per month too, I didn't realise that didn't extend to being out of the Country though. I was charged a standard text rate, plus a fee for sending it while I was out of the Country and then I was charged again for receiving the reply! :'(
I nearly fainted when I phoned up enquiring as to why my phone had been cut off, that's when they told me the DD had been rejected by my bank and how much the balance was. I asked if I could pay it over 2 months and have my phone activated again and was told "no", so I grudgingly paid with my AMEX.
The woman asked me what I had been doing to run up such a large bill, I was too embarrassed to admit I was dumb enough to think my free texts extended to outside the Country so I told her my friend had borrowed my phone for emergencies LMAO.