Mobile data upload speed barely above 0.00Mbps after 7.1 update

Hi, I've recently been experiencing abismal mobile data speeds on my iPhone 5 since I updated it to iOS 7.1 on Sunday.

Whenever I perform speedtests my download speeds can be fantastic, but my upload speeds are ALWAYS ridiculously low. It will start off and shoot up to 5/6Mbps and dwindle to 0.04Mbps on average... Which is unusable. I use my mobile data for FaceTime frequently, and there has never been an issue until now; I'm lucky if calls even connect.

I never had this problem before iOS 7.1, and, short of replacing my phone, I have tried everything.

What can I do?