[HTC Rezound] HowardZ:
Ok, I got a $1 prepaid T-Mobile SIM card with 10 minutes of talk and/or texts.

I put it in my Rezound using 4.03.605.2 stock rooted, s-off phone.

I got the SIM lock screen warning, so I went to bootloader and used the SIMLOCK menu item to load a config.dat file I got for free from the internet. However, it did not remove the SIM lock screen warning, so I suppose that is something of a nag screen to be lived with.

Here is where I got the config.dat to unlock the HTC Rezound:

http://www.sieempi.eu/blog/2011/09/22/universal-sim-unlock-for-s-offed-htc-devices-536

Unfortunately, I do not know if it helps or not since I did not try to actually use the T-Mobile SIM card prior to installing the config.dat file, and there seems to be no way to un-do it. It certainly did not help to eliminate the SIM warning screen. I do not know if it was in any way helpful for getting voice and texting working.

With the Verizon SIM installed, one can not modify or add APNs. Anyway, with the T-Mobile SIM card installed, switch to GSM/utms, and one can add and modify APNs. The Verizon APN automatically gets some modifications for T-Mobile, but will still have the APN Field set to VZWINTERNET and the APN Type is incorrect. One can add the T-Mobile APN information to a new APN or modify the existing APN, and then I got "E" for Edge speed on the notification top line on the phone. I sent a text message and received a text message.

I can not get any speeds faster than Edge. This might be because I do not have a data plan, as it is just a voice and text prepaid plan on the T-Mobile SIM card. Or it might be that the faster data modes on T-Mobile are not frequency compatible with the Rezound.

It was very difficult to find with Google, but here is a webpage with the frequencies and GSM/HSPA specifications for the rezound: http://www.webkitlab.com/#mobile-spec-root

It is very tricky to put the phone back into Verizon use. When the Verizon SIM is installed and the phone booted up, there will always be exactly one APN which is locked from modification. It will have inside it the T-Mobile APN (epc.tmobile) information that was last used with the T-Mobile SIM card. This will be the case even if you added a new APN for T-Mobile use, as it somehow ends up modifying the Verizon APN.

The solution is, with the T-Mobile SIM card still in the phone, switch the phone to LTE mode. Then go into the APN menu and change the APN to be VZWINTERNET. Then switch to the Verizon SIM card and it will work fine. The APN is locked from change when using the Verizon SIM card.

So, you should have written down the Verizon APN information and the T-Mobile APN information before experimenting with a T-Mobile Sim card, and will need to enter it when changing SIM cards. That's the only hassle, that APN information must be entered every time one will be switching SIM card, and the information can not be entered or changed while the Verizon SIM card is inserted.

I did some texting tests, but didn't do phone call tests.

Edge speed is supposed to be very slow - I think I've read 384 Kbps which is better than the dialup modem internet days, but still slow. So, I can see someone being economical and using a T-Mobile prepaid SIM card. $100 gets you 1000 minutes with a one year expiration. Personally, I rarely use even 100 minutes in a month, so it can last a whole year for $100. The negative side is that DATA use will be limited to when having WiFi availabile. T-Mobile does have a monthly plan with 100 minutes and 5 GB of fast data for $30 per month, but I do not think the Rezound works on T-Mobile's HSPA+ frequency, so this would be a waste to spend $30 per month and get Edge speeds. At least it appears this way to me.

So, I got a great deal of entertainment value from my $1 T-Mobile Sim Card.

This might help others,

Regards,

Howard