I'm replacing my old phone with a Samsung a50 and I had to get a new sim card for it, but when I try to change devices on the website it tells me to contact you.
Sorry, didn't read your post carefully enough, I only went by the post title. Were you at the Swap SIM page when you got the message to contact customer support?
There isn't anyone here from customer support, we are just Telus customers like you. Try using the online Chat fuction to contact customer support.