I have been receiving a high quality and reliable connection at my home from Koodo for the past 3 years, but last week the connection became poor - there is static and the call breaks up. There are only 2 bars displayed for my phone (which has not changed - Samsung Galaxy 6).
Alright let's try to isolate the issue. Restart your phone, toggle airplane mode, pull the Sim card out for a minute then back in. If you're still having issues see if you can put the Sim in another device and another Sim card in your phone. If you're still having issues moving the Sim, try it outside of the neighborhood. Is it only in your house ? Or outside ? When do you start having a good signal again ? If it stays bad then you will need a news Sim card. If its only around your house it could be a tower is down or acting sporadically.
Go into your settings, then click mobile networks - network operators - search for networks, it will then search for the closest towers in your area (this can take a minute to search) after the search is complete a lost of carriers will pop up and you will select koodo and then just exit the settings menu.
This has worked for me in the past to fix the weak signal issues so worth a try.