Use data-only sim with rezound

[korrect]

Hi,
I wonder if it is possible to use a Data Only SIM in my rezoned (latest RUU 4.0.3.605.2). I have tried Tmobile and AT&T SIM with regular voice/text and both worked fine with minor changes in APN and APN types.

With the data sim, I was able to send and receive text msg. Trying to make a call resulted in the standard warning "... can't make call on this line", which is obvious. The data sim is mostly used with my USB data connector plugged in a pc/mac, or MiFi hotspot. I can't seem to get it work on data with standard wap.cingular APN setting (this is a ATT SIM). Also tried various settings with wireless.cingular.gprs.com or wireless.cingulargprs.com as proxyetc etc with no luck.

So, does the Data SIM have different setting than the regular voice/text/data SIM?

Much appreciated of your help!