iphone 7 keeps changing my contacts default account from iCloud to one of my main email accounts

Recently, when I attempt to find a specific contact on my i{hone, I am often unable to locate it, especially after an os update. When I check my settings, my contacts default account has been changed from iCloud to one of my main email accounts. When I directly enter the person's number or find the business number online and call it, it registers as the name of the person or business. I have tried many fixes including switching contacts off and back on, going into the settings for contacts and changing the default account back to iCloud, then to make sure that it stays that way for awhile at least turning my phone off and then back on. Nothing seems to make it permanent.