Apart from the categories that aren't eligible, there is no way to turn off Simple Delivery... if you want to use a recorded delivery service, you would have to 'ignore' the Simple Delivery label, and buy your own postage, elsewhere 

Then you would have to replace the Simple tracking number with your own tracking number, and apply for a refund for the unused Simple label. Unless your buyer paid for the Simple label - then they would receive the refund.