How do I get my Huawei E3131 modem to work on my MacBook Pro 2013 (running OS X Mavericks)?

I have a one-month-old 13-inch MacBook Pro (running OSX Mavericks) and I'm unable to get the computer to recognize my Huawei E3131 external modem. I've tried downloading the MacBook Pro driver from the Huawei website (at http://consumer.huawei.com/en/support/downloads/index.htm?keyword=MobileConnectD river%20for%20MacBook%20Pro%202013), but when I try to install the .dmg file, I get an error message saying that the file is damaged. I've downloaded the file multiple times.

I emailed Huawei two weeks ago for support, but they never replied. I can't call their service centre because I am in Uganda, and they don't have a service centre here. Similarly, Apple seems to be under the impression that the continent of Africa doesn't exist, so I'm unable to get help from them either, so far. The folks working at my mobile internet provider are about as knowledgeable as a sack of hammers.

I've read elsewhere on Apple Support Communities that there is some compatability issue with the MacBook Pro USB ports and Huawei dongles, and that using a hub might solve the problem. Unfortunately I am in a rural area and can't find a USB hub.

I've used the modem on a brand new MacBook Air and it worked fine, and I've used it on a 2008 MacBook and it also worked. So what can I do?