If you are talking about RS3, then you can reset your defence, just under strict circumstances.
'Players looking to reset Constitution and Prayer must have level 5 or lower in Attack, Strength and Defence while players looking to reset Defence must have a total level of 10 or more in Attack, Strength, Magic, and Ranged.' [Source: RS Wiki]
If you are talking about OSRS, then I'm afraid nothing can be done.
When the unwanted xp bug happened did you apply within the time limit to get it rolled back? Just wondering if you made the time limit. I know it was taking Jagex a long time in fixing each account as it is a tedious process.The richest person is not who has the most. It is who Needs the least.