8446678744

Walmart Financial  in Canada does, but I don't know who handles collections for them.  The Walmart Rewards Mastercard® is issued by Duo Bank of Canada.
https://www.walmart.ca/en/financial-services/walmart-rewards-mastercard

No information on this number being one of theirs, so I would direct anyone to go to their website and find out from there and not trust the caller.

The bank would do the collections not Walmart.  Once the card is issued the store is usually out of the picture for payments.  The bank pays the store right away for the purchase and then assumes the responsibility of the debt.  The bank is also the one that approves the card not the store.  I would think that it works that way everywhere.  That way Walmart does not have to worry about collecting unpaid bills.  They have their money and the profit that went along with it.  If someone doesn't pay then the bank gets stuck.  That is one of the reasons the interest is so high on those cards.

Got a call from this number twice, they did not leave a message the first time, and the second time they left white noise. I phoned back the number and the automated voice message claims to be Walmart for their Rewards Mastercard and asked to input your whole 16 digit card number. I hung up and called the real Walmart twice and was told this number is not associated with them and they did not call me. I let them know about this number and that it is a scam. DO NOT give the people behind this phone number your information. If you get a call from them, hang up and call the number that is on the back of your card.

Peace out.

Wanted WalMart Mastercard numbers, including 3 digit #on back.
Would NOT give a reason. Asked several times. Then hung up.

I think it’s for their MasterCard

Once again, Walmart does not issue their own credit cards.  Therefore Walmart has nothing to do with the card other than to accept it as payment when you check out.  Any collection calls would be coming from the bank that issued the card and not Walmart.