As far as I know,your cell phone also should support the 3G service...then only it will accept the 3G sim that you insert..To improve your internet in your mobile..try the following tips;
*Using a mobile internet connection in a congested room can decrease the connectivity hence try to find a near by HotSpot and use since its more active.
* You can try using the mobile internet Off Peak hours thereby avoiding the traffic.
*Try updating the Mobile firmware and keep checking if there are any updates for your phone.
*Try to purchase a booster/antenna which may capture more signals.
*Do not install lots of software on mobile.
*If you are interested only in text then there is option in mobile to block images. That will give you fast speed and will have less charges as some providers charge per KB.
*Do not access other applications while surfing.
After you have tried some of this,try your connection again using Scanmyspeed.com and see if it's running any faster.If you are not still satisfied try to upgrade the data plan or switch over to a 3G supported cell phone and access the fast 3G network.