Qacer
you should find the "radio taxis" number advertised somewhere online, before coming to Poland, or maybe even at the airport, 'm not sure about cell phones, but from a land line you just use 4 numbers instead of 10, normal numbers in Warsaw are like this (0-22) 1234567, while radio taxi may have a following style phone number: 9494 or 9559 (probably even without the (0-22) for Warsaw, but not sure)
Online, I've found rates as low as 2.45PLN per USD, and as high as 2.65 PLN per USD
you better check National Bank of Poland site before buying, today's rates are
dolar amerykański 1 USD buys at 2,8198 sells at 2,8768 - any good "kantor" should have similar prices (or even better for the client), but there's been some fluctuations on the international stock markets recently, so I guess currencies exchange rates change a lot every day, (4 weeks ago the price was 2,7286 (buys) / 2,7838 (sells))
nbp.gov.pl/Kursy/KursyC.html