T-Mobile 2G and 3G

Yesterday, I called T-Mobile to ask about their service, specifically the 1900MHz 2G mentioned on their website. I also asked about the 3G hotspot in their essentials plan. Long story short, after awhile on the phone, I was told that I can use a 3G phone on their network, and it will work on 3G. They even specifically told me that the iPhone 4S is the oldest phone they support. So, can I in fact, use 2G and 3G phones on T-Mobile’s network in the USA? Thanks in advance!