I read both articles and didn't see SMS banking mentioned anywhere. NFC, Mobile Internet, etc... not sms. So I did a bit more digging and found items such as: SMS Banking - Top Up via SMS which do discus sms and digicel.
Lets be clear, sms is not in any way, shape or form secure.
But from the articles I've found thus far, you can't do very much through sms. Most possibilities include checking balances and mundane things like that. The only possible transaction I've found is the ability to add money to a TopUp account from an already setup/linked Visa/Mastercard/etc. So yes, one could move money from one account you have to another account you have through sms. Not much of an attack vector. You'd have to compromise the TopUp acct/card/phone as well, so if you had your wallet/purse/phone stolen you'd be at a high risk. But one is normally at a high risk when these items are stolen.