What's the difference between quad band and tri band?

You have not mentioned the model number. However, there are phones with different capabilities as far as the frequency (bands) is concerned. Some are quad bands, meaning there are four frequeny ranges. These can be used the world over if unlocked. Some phones have lesser bands. They can be used if subjected to similar bands. If your phone is anything but quad band then it can not be used everywhere.

I see that this had been a while. The reason that your Sim cad doesn't work could be various: 1. Make sure that your phone is quad band, if it's a tri band then make sure that ATT works in 1900mhz. If it works only in 850 and your i68+ is a tri band, (which is not suppose to) then it will never work. As far as I know all i68+ original are quad band, some fakes i68+ are sold as quad band but are actually tri-band. 2. If you ATT sim card is a 3g card, it won't work either. These phones are not yet equip to work with 3g. I hope this clear up at least a little of your doubt with the Sciphone.

http://mobileinfo360.blogspot.com here is your solution

This phone is only Tri-band and made for Europe only, it is not Quad band which means it has the 2 European frequencies but only the one odd US one so you probably cannot get access because the phone is missing the frequency. Anytime you buy a phone on-line make sure it is either 850Mhz/1900Mhz for US or that it is QuadBand. 850/900/1800/1900Mhz which means it works in all countries on all networks.

it is only tri band dude. it night not work in your area if you dont have the right signal band.

I had the same problem so I went into Menu-Settings-Network Services-Band Selection. It should then give you the option to select two different types of GSM Bands or Quad Band. I found that Quad Band works for me, but the GSM 850/1900 worked as well. Hope this helps!

yes,your L6 phone is only triband,its work only on frequencies,900/1800/1900mhz.now if your network provider is using 850/1900 mhz so the 1900mhz will work,and remember the highest frequency that we have the shorter the distance we get...hope it will help your problem....

there is nothing that you can do actually , you need to buy a quad-band phone.......

the W850i is a tri-band phone...meaning it should be working on 900mhz/1800mhz/1900mhz band...if 3 and orange networks may be working on 850mhz band...so you need to get a mobile that pick up the 850mhz