How to turn off bluetooth PERMANENTLY on iphone (i.e. until *I* re-enable it)

I have two iOS devices, an iphone and a macbook pro. Plus two bluetooth devices I commonly use: one for piping music to my home stereo, and one small portable speaker (for the bathroom, or taking to parties/picnics/etc).

A typical attempt to connect to, for example, my stereo, goes as follows. I turn on the stereo, hold down the on button of the bluetooth thing until I hear its little "on" sound come through the speakers, and then go to, let's say, my laptop, to connect its bluetooth to that device. Except, I can't, because voilà it has already connected to my phone (so impressive, no wonder they call them smartphones).

Okay, so I disconnect my phone from it, and then go to connect my computer. Except now something's messed up with the device; it's in a confused state and it won't connect to anything. I have to turn it off and back on. Now maybe it will work or maybe it won't. Maybe I have to turn off bluetooth on my laptop and back on too? Or both? I try various permutations of turning things on and off in different orders. Maybe I have to leave it off for a period of time before turning it back on? Sometimes I have to power cycle my whole laptop to get its bluetooth working again. I especially had to do so in the past; the bluetooth on my mac was very buggy for the first couple years. If I am trying to entertain a friend or god forbid allow them to connect to my stereo with their own phone, it usually ends up in embarrassment and giving up.

But didn't I turn bluetooth off in the settings menu yesterday on my phone just so this wouldn't happen again? or didn't I turn it off earlier before it restarted for an update? This is why I turned it off in the settings menu instead of in that more convenient way that says it automatically turns back on "tomorrow." So why/how is it back on?

When I search for answers, apparently this behavior is intentional on Apple's part? I don't really want to hear a justification for that, please spare me the inanity. Just, how do I make this process more predictable (without buying anything or any further inconvenience).