Is it possible to downgrade from 5.1.1 to 5.0.2?

I recently upgraded to 5.1.1 on Telus and now I am having the network connectivity issues that have been reported on other threads. Specifically, when I am on WiFi and have LTE enabled, all phone calls go directly to voicemail when someone tries to call. If I turn of LTE it seems to work fine.

I am assuming it's an issue with LTE and 5.1.1 so just wondering if anyone knows of a way to downgrade to 5.0.2