Hi Are you sure you bought a goodybag and not just added airtime credit? As it sounds like you just added airtime credit.
Airtime credit and goodybags bundles are two different things. Adding airtime credit will not apply a goodybag automatically. A goodybag is bought direct using a credit/debit card or airtime credit can be exchanged for one
you can simply click 'auto recur' your goodybag? This means the goodybag will automatically renew every month without you having to worry, click here: https://giffgaff.com/profile/payment-details#goodybagsettings
The airtime credit is used for calls and texts not included in goodybag allowances e.g. 084, 087, 118, 09 and International numbers.
See this https://giffgaff.com/support/top-up-and-balance/credits-and-goodybags-purchase
link to learn more about airtime credit and goodybags.
Hope this helps you