Free minutes lost after contract change

I have recently upgraded my phone contract. I was on RedVantage package but had lots of minutes which I didnt finish. I was sitting with a balance of about 1300 minutes. I then asked them to switch to a package with less minutes. The agent assured my I can still use my minutes that I currently have. After the plan change my 1300 minutes with I have already paid for was dropped from my contract, and the contact center just informs me sorry he should have told you. Did I know i would be losing all my minutes I would not have changed to the current plan. I want the minutes I have paid for to be credited back to my account for use.