Billing issues after account closed

I have closed my mobility services with Telus in January of this year (2024) due to moving to other country. I called the customer service. Was redirected to the billing department. I’ve paid all the outstanding balance and was told everything was ok to close the account. I’ve received now in May an email from telus telling to pay outstanding amounts and threatening to be taken to credit collector. I’ve been trying to respond the email ( as can’t call Tellus because I’m in Europe ) and haven’t received any response. How can I get ahold of them and again have confirmation of payment I’ve already made ?