Hello CryptoCoinoisseur,
Calls coming to or displayed on other devices would happen by enabling Calls on Other Devices or iCloud Drive.
On the iPhone under Settings > Phone > Calls on Other Devices, if you have that enabled then phone calls will be sent to all other devices you have it enabled on. Meaning that when someone calls you, both your iPhone and iPad would ring.
In Settings > Name at the top > iCloud, if you have the iCloud Drive on, then your call log will show on any device iCloud Drive is also enabled on. This would mean that even if you have the Calls on Other Devices option turned off, your call log will still show on other devices even though they aren't receiving incoming calls.
View and delete the call history on your iPhone
Cheers!