Sorry to hear you're having trouble with your ISP throttling your speeds. While a VPN can help bypass throttling on both cellular and WiFi networks we are not able to offer a guarantee that it will in all cases as there are many different factors on the ISPs end that can impact this.
That said, you can try connecting with an OpenVPN connection to see if there is any improvement and select a server closest to your physical location. Here are the setup instructions for OpenVPN on iOS: https://support.goldenfrog.website/hc/en-us/articles/203815486-VyprVPN-OpenVPN-App-for-iOS-7-
Unfortunately, if you're still experiencing throttling with the steps above we do not have any further recommendations we can offer as your ISP is likely throttling encrypted traffic.