Thank you for the info!
We seem to have some issues with certain LTE providers, and we are still trying to figure that out. You can change the IPv settings with certain providers on certain Android phones, which means the problem can be avoided altogether.
Can you try this on your iPhone and see if it works?
Settings > Cellular > Cellular Data Options > Voice & Data > 3G
Also, if you don't force 3G on your Samsung, can you connect or not at all?
Thank you so much for helping us work this out!