My iPhone doesn’t wanna update to iOS 14

These are the iOS options based on iPhone Model --> Learn how to--> Update your iPhone, iPad, or iPod touch - Apple Support

• iOS 14.3 —> 6S / 6S Plus, SE (1st Gen and 2nd Gen), 7 / 7 Plus, 8 / 8 Plus, X, XR, XS /XS Max, 11,11 Pro /11 Pro Max, iPhone 12, 12 Mini, 12 Pro, 12 Pro max
• iOS 12.5 —> Final release supported on iPhone 5S, iPhone 6/6 Plus, iPad Air, iPad Mini 2, iPad Mini 3 and iPod Touch (6th generation)
• iOS 10.3.4 —> Final release supported on iPhone 5 and iPad (4th generation) Wi-Fi + Cellular iOS 10.3.3 —> Final release supported on iPhone 5C and iPad (4th generation) Wi-Fi
• iOS 9.3.6 —> Final release supported on iPhone 4S, iPad 2 Wi-Fi + Cellular, iPad (3rd generation) Wi-Fi + Cellular, and iPad Mini (1st generation) Wi-Fi + Cellular
• iOS 7.1.2  —> Final release supported on iPhone 4.
• iOS 6.1.6 —> iPhone 3GS and iPod Touch (4th generation) only
• iOS 4.2.1 —> Final release supported on iPhone 3G and iPod Touch (2nd generation)
• iOS 6.1.5 —> Final release supported on iPhone 3GS, and iPod Touch (4th generation)
• iOS 3.1.3 —> Final release supported on iPhone (1st generation) and iPod Touch (1st generation)

Updates don't work that way (no one sends you anything), you check for updates and initiate from your device.

If you have an iPhone 6 Plus, you cannot run iOS 14.. You can run iOS 12 (latest is currently 12.5)

If you need newer iOS, you'll need a newer iPhone model.