iMessage on my iMac and MBP show old phone numbers for my Contacts

I have long since deleted old phone numbers for my Contacts, but they always still appear in iMessage on my iMac and my MacBook Pro. My Contacts are synced on my iCloud and the old numbers don't exist anywhere. I have tried unlinking iMessages from my iCloud account and relinking, and all sorts of different tactics, and still, old phone numbers pop up when I type in my friends' names to start a new conversation. Their new numbers pop up, too, but sometimes I accidentally text the old number. How do I get the old numbers out of my iMessage?