question about usa sim cards
 

The credit in usa sim cards has a validity of 30 days... But after these 30 days, I lose only the credit or also the sim dies?
Sorry for my bad english!

Card validity dies after 30 days :(

With tmobile, the sim dies 90 days after the credit expires. Also, tmobile sim cards can have a validity up to a year from last topup. It just depends on what level it is and how much it has been topped up. Check their website for more details.

And ATT sim card? Only 30 days? After this this I lost also the number?

USA prepaids are notorious for their short lives. Many must be topped up every 30 days. The only one with anything like decent lifetime is T-Mobile after you add $100 worth of credit (a.k.a. "Gold Rewards"). After that you only have to add a minimal ($10) top-up every 12 months.

There is another alternative: SpeakOut from 7-Eleven. 7-Eleven is a chain of variety/convenience stores. You have to buy the phone from them (e.g. a Nokia 1600) in order to get the SIM, but the airtime lasts 1 year. If you already have a 850/1900 band phone you may be able to buy only the SIM on eBay. Once you have a SIM you can add airtime in increments as small as $25.

They run on AT&T's GSM network using an MVNO, Ztar. Their website seems to be under construction right now so I don't have all the details, but I do use their Canadian product which is similar.

The SpeakOut website has been "under construction" for years. It's true, it has a 365-day expiration, but as you have to buy the phone (there are no SIM-only kits) the upfront cost is quite high. Might as well get a v195 from TMO and go Gold Rewards immediately.

The Canadian Speakout is also an offer that looks good at first glance. Except that the 365-day expiration is not all that it seems -- as a lack of account activity for 120 days will end the account. Since there's no roaming, it's not possible to keep it going unless you're in Canada every 2 1/2 months.

According to this thread on HoFo, as little as $20 with $10 airtime. The phones that come with US SO are locked (the ones in Canada are not.) And AFAIK you can top up airtime using AT&T's website so you can keep this SIM alive from overseas.

Where did you get that information? AFAIK there's a 99¢/month "911 fee" but the card lasts a full year providing there is enough airtime credit. Once the year ends you have something like 90 days to top it up before the SIM expires.

Actually the only way to top up the Canadian SO SIM is to buy a voucher at a 7-11 store in Canada and then validate it from a SO phone. So it's effectively useless to anyone outside Canada. Unfortunately there are no good GSM options for visitors to Canada thanks in large part to Rogers' monopoly. (Perhaps the best option for visitors is to use a US T-Mobile SIM then pay 69¢/min to roam in Canada :( )

OT? - 2003 visit to Canada
 

Probably off topic....

My wife and children were in Canada in 2003. I had purchased a prepaid Fido SIM from eBay USA. That worked fine. After they returned, I sold it on eBay to someone else. At that time our T-Mo prepaids did not roam in Canada.

I take it the situation has changed since then. I think Rogers and Fido are now one company. I am a bit surprised your regulators would allow such a merger to result in a monopoly.

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As to the US GSM prepaids, I often look at eBay.de. You can always find ATT or T-MO US prepaids being offered there. I don't know how well they sell, but I suspect there is some demand for them. Thus, if a visitor purchased a US prepaid SIM, I think it would be possible to sell it on his/her native eBay or elsewhere to someone else rather than try to keep the # alive. The $100 upfront investment for 1000 minutes might not be everyone's cup of tea.

I made a very costly mistake buying 2 Malta prepaids and trying to keep them alive. I lost one where I had invested > $50 and sold the other at a huge discount. Would have been cheaper to buy new ones or use my international SIMs.

Stan

Yes Rogers bought Fido and now they are both the essentially the same. There are two developments that may open up Canada to more GSM competition:

1. There is a spectrum auction in progress. Something like 40% of that spectrum is designated for new players only. It's highly unlikely that the winner of such an auction would use anything but GSM. Also, the incumbent wireless providers are required to lease towers and cell repeaters to new players for at least 5 years at "reasonable" rates in order to give them a chance to succeed.

2. Telus, the main western Canadian telco, is currently CDMA-only. However there is speculation that they will start to convert their network to GSM, starting in western Canada, in order to participate in lucrative roaming revenue from foreign visitors to the upcoming Vancouver Olympic games. (Rogers charges something like $2 or $3 per minute for roaming and gets away with it because there is no GSM alternative carrier.)