If you’re like most people, you love your iPhone, but you don’t like the high phone and data fees of AT&T.  If you want to use your iPhone on T-Mobile and take advantage of their lower rates, here’s what you need to do:

  1. Get an Unlocked iPhone.  If you’re out of contract with AT&T, usually after 2 years, you can have them unlock your phone.  With AT&T, you can find out about eligibility at: http://www.att.com/esupport/article.jsp?sid=KB414532#fbid=h0oX5NEasZY  Alternatively, buy an unlocked iPhone from Apple directly (costs an extra $450 from the subsidized price) or through a site like eBay, Amazon.com, etc.  Make sure it’s a GSM phone if you want to use it on T-Mobile.  I would recommend buying an unlocked iPhone if you don’t have one already.  The savings over 2 years will more than make up for the extra $450 you spend. 
  2. Get a SIM card from T-Mobile.  You can request this from their website or at the store.
  3. Trim the SIM card to fit your phone.  All you need is a sharp pair of scissors.  Take out your old SIM card to examine the size.  Make sure you don’t cut too much or the new card won’t fit the SIM slot.
  4. Call T-Mobile or use their online forms to sign up for new service.  They are currently offering – through their website only – a no-contract $30/month plan that gives 100 minutes of phone time and 5 GB of data.  On the phone, you can get a 2-year plan for approximately $50/month that is very similar to the base plans that AT&T offers.

Here are a couple things you need to be aware of before you make this switch:

First, because T-Mobile uses a different wireless spectrum than AT&T, you may or may not get 3G on your phone after you switch.  T-Mobile is currently expanding its 3G spectrum to include the iPhone, but it may take a couple months before your area has it, in which case you will be on the Edge network, which is significantly slower. 

Second, Visual Voicemail does not work the same after you switch.  You will need to set up your voicemail through T-Mobile and then call that number if you have a message.  Supposedly T-Mobile is working on an app for Visual voicemail, but it is not currently available as of today.