Deceiving service and inability to cancel unused services

By pushing *111# one can purchase data bundles for example. However this service uses trickery to sell you more than you want. By falling in this trap I accidentally purchased a data bundle I don't require after already purchasing the bundle I do require. I called customer care to cancel it and it's not possible according to the operator. The *111# service should not offer one more after a purchase and one should be able to cancel purchases especially when not used by the client yet. It's a clear tricking scheme and unfair. After being a subscriber for 20 odd years I deserve to cancel a mistake I don't need please.