Hello There… It’s The Second Time After Happening… My Vodafone Credit Was Not Registered Properly;?

therefore all the credit went off of it just a few days after my mother topped me up with €30.00 …
I am on Pay As You Go Vodafone… I also took the chance to make use of the IOU service which offers a €4.00 Top Up when your credit is insufficient. You just have to send SUPER to 50223 and after a few seconds you receive an automated message saying you received the €4.00 credit which goes into minus credit, the more you need to use it.
What am I supposed to do about this? Any solutions, please?