I bought storage but it hasn't come up on my iPhone

What do you mean by 'it hasn't come up'? Come up where?

You won't magically see 200GB more space on your iPhone or iPad - that isn't possible. It sounds like what you've done is increased your iCloud storage to 200GB. This can be used to offload content from your Mac/iPhone/iPad, and to share data across devices.

You can configure devices to automatically offload little-used data to iCloud, which has the effect of giving you more usable space on your device - check your iCloud settings on your device to enable this.

https://support.apple.com/en-us/HT206504

I’m having the same problem, when I upgrade it doesn’t show the upgrade in my settings it still says I have 5gb & that I need to upgrade.