What is the moble network when u can call all the networks?

Is it normal for the Blackberry Bold to be switching mobile networks constantly (3G to EDGE to gprs)?

• I just bought a used Blackberry Bold from someone yesterday. AT&T service, and no data package plan (no internet). The problem is that this phone will constantly change networks from 3G to EDGE to gprs, sometimes it takes 2-3 seconds to do so if it will say "Searching for network..." before switching. Sometimes when I call or someone calls me, it wont go through because the phone will be switching networks. But if I am actually having a conversation on the phone, then my call won't get dropped and the network stays the same. Yesterday I was having a problem with the texting: after a while the messages just wouldn't get sent anymore and said "pending", but after taking the battery out and back in it got fixed. Also, this morning when I woke up the phone had no service, so I had to turn it off and back on and then it was fine. Please give me any suggestions you can to help... I need to know if there is something wrong with the phone itself, or if something else needs to be done to fix it, or if this is normal with the Blackberry Bold. Thanks!

• Answer:

  as far as the type of connection goes its normal, i have the 8900 and its always on EDGE but when i go to one certain side of town it switches over to GPRS and my phone still functions properly