We’ve just been given a little more information about the Walmart Family Mobile service we told you about several days ago. Here are all the details — some new and some old — that we’ve been given: The phone service will cost $45 for the first line (which includes unlimited calling and texting) and $25 for each additional line; you can add up to five lines. The web portion of the plan will be a shared bucket that rolls over from month to month. If you have a 200 MB allowance, and only use 50 MB in the first month, your 150 MB of leftover data are still available. Data allowances will be purchased on pre-paid data cards named WebPakTM cards. Calling to 14 major international cities (including cities in Canada, Mexico, and Japan) will be billed at 5-cents per minute (the $0.05 is billed against the value of your WebPakTM card). You will be allowed to activate any unlocked U.S. GSM cell phone on Family Mobile for a $25 activation fee and you can pre-pay your bill with a credit or debit card at any Walmart store nationwide. On Monday September 20th, the service will launch with the following phones: Nokia 1661 for $35, Samsung t139 for $50, Samsung t749 for $150, and the Motorola Cliq XT for $250. There will also be a Samsung slider-device, similar to the Gravity, available for $100. The ability to BYOP (bring your own phone) seems pretty generous. What do you think? Perfect spot for a Nexus One?