Is your goodybag expiring tonight in which case read the following.
Sorry but you cannot buy another goodybag after 7pm on the day a live one expires. You will be able to get another one in the morning from around 9am onwards (maybe later).
Until then you will need to use credit for calls and internet access after approx midnight when the goodybag expires/d (so maybe turn your data off until you have bought the goodybag)
In future to get around this you can queue a goodybag (just buy another one anytime before 7pm on the live expiry day) and the queued one seamlessly replaces the live one between 10pm - midnight on the expiry day.