user8167: I would like to state that I am not familiar with the whole cellular connection thing. But I was wondering if the SIM900/or/SIM900A is 3G and will work with PTel Mobile.
I need this Arduino to be able to travel and needs to connect to every PTel's tower. Will I be able to connect to 3G or only the 2G and the 1G networks?

user11285: First of all if you are in USA you cannot use SIM 900A since it supports only Dual frequency bands.(900,1800 MHz)it supports only Asian region countries. 
According to Wikipedia, PTel Mobile supports only GSM 850/1900 frequencies. 
so SIM 900 supports( 850,900,1800,1900 MHz ) you must use SIM900
Considering about the speed you cannot obtain 3g, 4g speed since GSM Shield(SIM900) provides maximum of GPRS class 10: max. 85.6 kbps (downlink) so, 
It will able to connect but cannot get such speed in 3g and 4g.

8167: <p>I would like to state that I am not familiar with the whole cellular connection thing. But I was wondering if the SIM900/or/SIM900A is 3G and will work with <a href="http://www.ptel.com" rel="nofollow noreferrer">PTel Mobile</a>.</p>

<p>I need this Arduino to be able to travel and needs to connect to every PTel's tower. Will I be able to connect to 3G or only the 2G and the 1G networks?</p>
 11285: <p>First of all if you are in USA you cannot use SIM 900A since it supports only Dual frequency bands.(900,1800 MHz)it supports only Asian region countries. </p>

<p>According to <a href="https://en.wikipedia.org/wiki/List_of_United_States_mobile_virtual_network_operators" rel="nofollow">Wikipedia, PTel Mobile</a> supports only GSM 850/1900 frequencies. 
so SIM 900 supports( 850,900,1800,1900 MHz ) you must use SIM900</p>

<p>Considering about the speed you cannot obtain 3g, 4g speed since GSM Shield(SIM900) provides maximum of <a href="http://www.simcom.eu/index.php?m=termekek&amp;prime=1&amp;sub=40&amp;id=0000000147&amp;page=1" rel="nofollow">GPRS class 10: max. 85.6 kbps (downlink)</a> so, </p>

<p>It will able to connect but cannot get such speed in 3g and 4g.</p>
