I've read through several thread with similar titles and I can't seem to find anything that pertains to my problems, or I might have missed it.

Before I tell you my issue, I would like to give some information first.
I'm using T-Mobile's $5.99 T-Zone plan with the epc.tmobile.com APN. The area I'm in does have a stable 3G coverage, I'm in NYC.

Anyway, here's my issue. When I'm connected to my data connection, after about 2-6 minutes from connected, I would get a message in the yellow bar saying no "cellular data available". On the top, where it shows the signal bar and connection type, it would be replaced with a sim card with a red line going across it. Basically this means there is no sim card in it(obviously there is one in it). This situation would last for about a second or two. After that, the cellular signal is reconnected. Then when I try to reconnect to my data connection, no matter how long it searches, I can't reconnect. The only way I can reconnect is restarting the device. Sometime, I should say most of the time, the problem persist if this problem shows up. If the problem does persist, no matter how many time I restart, the connection would not last through that 2-6 minutes interval before it would be disconnected again. The funny thing is that this happens in areas where I can use my data connection without issue and this happens frequently, but at random.

I can almost conclude the fact that it's not my network's issue because I've tried several phones and I don't have this disconnection issue.

I do hope that I'm not posting this in the wrong section.