It may depend on the method they use to send the SMS. The tool they are using may be blocked for spam, or may be using a standard not supported by Koodo. Do you know if others are receiving such texts, and if they are also using Koodo, or another carrier?
Do you receive regular SMS from family members or friends? Do you have data on in order to receive MMS. Sometimes there are settings in your phone to block certain kind of messages. Did you look at it or tried to change it?