Airtime used when there is bundles in place

I bought a 10min all net voice bundle from telkom, they send an sms informing me that the bundle have been loaded, I continued to make calls only to discover that my airtime was used. I contacted customer care who informed me that I have to disable the out of bundle setting and the problem is on my side. I do not wish to disable this feature because I don't want to be interrupted when my bundle is depleted it clearly states that it will start using my airtime after bundles are depleted. Customer care seem to have a no care attitude.I spend at least R200 a month on bundles and this is the second time this has happened.