I get phone messages deposited as a text message on my iphone....i'd like it to stop

Oy, this is making my head hurt. The very well meaning advice about clicking the three dots to get to the voicemail app ONLY WORKS ON AN ANDROID PHONE.

I’ve seen this problem time and time again on these forums. iPhone user asks for help, Android user sends them on a search for settings that don’t exist on the phone in question. 

I know you're only trying to help, but for future reference just know that iOS has visual voicemail built into the operating system. I am less tolerant of T-Mobile support who frequently seem unaware that half of their customers are using iPhones.