Managed to stop these calls. Got three calls a day from them, and a message from them on voicemail each day at the same time:
"It is very important that you contact Citi regarding an important matter with your Home Depot account. You may visit us online at myhomedepotaccount.com at any time. You may also call us at 1-866-458-7619. Any agent can assist you. Thank you."
Called them back at the 866-458-7619 number and told them this is a business line which hasn't been used for incoming calls for about 7 years since the person who had the line retired, so they must have a wrong number. Told them the number they dialed, and they said they had it on an account and would take it off. (I had also contacted the retired person, and they don't have a Home Depot account, but I didn't mention that.)
As a result, the calls appear to have stopped. Haven't had a single call from this number since (or the other numbers with this same message, including 877-437-1985). I have no idea who I was really talking to, or whether they are actually affiliated with the companies named, but they did have enough integrity to make a change so that their system stopped calling.