what do I do when I get kicked off wifi when i close my iphone

When you say you have to manually connect again, does it require you to use a username and password? It could be a captive network, and you would need to contact your IT department about that. Not all public captive networks support auto reconnects, but they should not require the username and password right away. Usually you get some time period before you are required to log in again, but IT could explain that. They are in charge of the network.

It is normal for the iPhone to disconnect from wi-fi when the phone locks and is not actively using wi-fi. However, once you open the phone, it should immediately reconnect.