Why can't I delete more than 3 Comcast voice messages and even then, all three are not deleted?

Hello..

I recently had an occasion to delete 28 voice messages that had been hanging around.

I decided to use the voice prompts to go through the messages one at a time using my phone. Once the message header was stated and the start of the message was heard I would do a '33' to skip to the end of the message and then do '7' to delete it.

I would then get something along the lines of 'Next message...' and go through the process once again.

What I found is that after doing this 3 times in a row, the voice prompts would stop after deleting the 3rd message. 

I would have to hang up and then dial back in with *99 and go through the process for another 3 messages, hang up, call back, etc.

What I also found out is that even though I would go through 3 messages, and the voice prompts would say 'message deleted', when I dialed back in the count of messages would NOT be decreased by 3 messages! Sometimes 1 message would be deleted, sometimes 2 messages. Rarely 3 messages would be deleted!

Why doesn't the voice prompts when you dial in to take care of voice messages work correctly?!

Paul