Goodybags allow for calls and texts to standard UK landline (01, 02 or 03) and mobiles. Any calls or texts to Non UK number would be charged, as would any premium rates calls.
Standard SMS texts are free but MMS (multi media texts) are charged at 16p per message (some older phones convert emoji into MMS - check yours).
Goodybags are for UK use mainly although can be used for short periods of time in the EU.
Other areas that could be taking your money is if you have been unknowlingly enrolled onto a premium rate text number service - these would take anything from £3 or more from your credit each time.
Hope this helps?