Virgin UK has hardly any coverage in South America, 02 UK is a lot better in that matter, but I'm not sure whether they provide data service as well. Telfort NL for example has roaming in most of those South American countries, but doesn't do data in those countries. I just mailed 02 customer service. I still not sure if they charge in 1kB increments with pay as you go either. I just downloaded mobisms to my phone over GPRS, but mobisms can't connect with the server packetinfo or something is failing
mobisms filesize of sms should be less than 600 bytes. so that would be 1 kB.
Active sims NL Telfort, KPN, Vodafone, TrendCall, T-Mobile
DE Simyo
CH M-Budget
PE Claro
INT Air Baltic Card, GeoSim
Non-active sims NL Qick, Easymobile, Tele2, Simyo, Rabomobiel, Vectone, UPC, GT Mobile, Orange, Hema, Lycamobile, Carey
TZ Celtel
Malawi Celtel
Zambia Celtel
SA MTN, Vodacom
INT UM, UM+, Go Global Sim, Max Roam, 09 Sim