Using my super old GSM phone

[Jerboy]

I have an old Motorola phone formerly used on Voice Stream. It takes a credit card sized SIM card. It's a mid 90s phone and this thing really is huge. I would like to use it with pre-paid just for novelty.

First, how can I unlock the phone and how do I get it to say "enter code now"?
The manual says there's an eight digit SIM release code. Is there an algorithm for getting this code?

Where can I get a credit card SIM size card with $10 or less worth of air time and how much do they cost?($10 or $10+card?)

[njsvrzncdma]

all sim cards come credit card sized. the "sim" breaks out to fit into regular phones. sims are usually 20 bucks i have tmobile sims. however theres no time on them it will cost 30 bucks for the prepaid kit from us. that gives you 30 dollars worth of airtime. after that you can buy 10 dollars of time as you need it. so all in all it will cost you 50 to get started from tmobile. oh and for the unlock code when you put in another carriers sim card it will ask you for the subsidy code. you can get them from ebay for like 10 bucks or less. also in the marketplace forum a few people there can do it.