I dont think so. Your phone number is matched to the ESN number of the phone. I believe there is one ESN for each phone.

Yes it is possible. You can buy a separate slide in piece that takes a second Sim card. This applies to phones with Sim cards obviously

I have talked to all carriers and no-one offers two lines on a single cell phone. Yes you can get a cell phone with 2 sim cards as stated above, but only one number can be active at one time... Whoever is first to market with this feature is going to do well.

If you witnessed this maybe someone had calls forwarded from another number.

1) "A dual SIM mobile phone is one which has two Subscriber Identity Modules (SIMs). Dual-SIM adapters are available to allow cellphones to contain two SIMs, and to switch from one to the other as required. Some phones are designed to work with two SIMs, both of which may be active at the same time. Dual-SIM operation allows the use of two services without the need to carry two phones at the same time. For example, the same handset can be used for business and private use with separate numbers and bills; or for travel, with an additional SIM for the country visited." Source and further information: http://en.wikipedia.org/wiki/Dual_sim 2) "Two cellphone numbers and only one phone: for many who tote around two phones, one for work and one for private use, that may sound too good to be true. Though few people know it, there are two ways to get rid of that second phone while keeping two numbers. The first option is to buy a small device, called a dual SIM card adapter, that when inserted into the phone allows the handset to carry two SIM cards - and therefore two phone numbers - at the same time. The other option is to have a second number added to an existing SIM card through your carrier. The type of dual SIM card adapter needed depends on the make and model of the phone and can cost15 to50, or $18 to $60. A SIM, short for subscriber identity module, is essentially a small piece of plastic with a computer chip in it that goes inside a GSM phone. The chip holds personalized information, including phone numbers and billing data. The device, which is normally inserted between the battery and the rest of the phone's electronics, is made mostly in China and can be hard to find in Europe unless acquired online through companies that sell mobile phone accessories. They work only on GSM phones. One reason the dual SIM card device is not widespread is that mobile phone operators do not want to share their clients with competitors. Giving customers the possibility to easily use two SIM cards opens the opportunity for them to have cards from different companies." Source and further information: http://www.iht.com/articles/2005/10/16/business/wireless17.php Further information: http://forums.macrumors.com/archive/index.php/t-228793.html http://reviews.cnet.com/4520-3504_7-5535376-1.html

Yes you can have 2 numbers on 1 cellphone using a service call Proxycomm. It works with your existing phone service... at&t, verizon, t-mobile. Check out the information further at their website. Features includes: - have 2 or more numbers on your existing cell phone or landline, each with its own voicemail. get 1-800 numbers or numbers with any area code you want, regardless of where you live. - get new features like call screening and call recording, have calls ring on multiple phones at once, advanced voicemail. - unlimited national calling, wholesale international rates, no new contracts, no special equipment, and no credit checks required. - use your existing cell phones and service, your landlines - even your computer for this service. - Transfer a live call from one phone to another. I currently have the service, it is really great. I decided to become a distributor with this Proxycomm because there is great demand for the service and I feel the service has a great future. People have been coming up with great creative ways of using this service and maximizing this service everyday. Some examples are: - include Proxycomm as 1 of your 'Favorite 5" (t-mobile), 'Friends & Family' (Verizon). By doing this you extend your fave-5 and your F&F service through Proxycomm to endless numbers. - in the near future Proxycomm services will expand into other countries, you can get a local number in any country you call often so friends and family can call you on YOUR local number in any country of your choice. As time progress.... there are new services, new countries being added to the service... this technology has endless possibilities. If you get the service and come up with new ways of utilizing the service be sure to let us know...! Need further info... visit our website: http://goproxycomm.com/aawhyte1

Yes go to secondvoice.com - it works and you don't need a data plan or some ghetto Voip software that sounds like crap. SecondVoice is a great deal and works on any cell phone.

I don't know if civilians can or not, my Iridium has three numbers corresponding to command levels. +5

It can be.

you could have any number of lines forwarded to your phone. But having TWO numbers SIMULTANEOUSLY active on one phone would be quite a trick.