I have had my magic jack for 2 years. It doesn't work well with my sprint air card on my lap top, but it works fine on my IBM tower and the air card. I use it most at home through the DSL connection and it works very well. I do customer support and call all over the US and Canada. There are some telephone end connections that will not accept a magic jack call. Small telephone offices, make their money on calls coming into and going out of their offices. I use my cell phone or regular phone line for all calls that I can't use the magic jack for. It has saved a ton of money. Good Luck.