CO Detectors are expired and beeping!

   I have 3 CO detectors in my house.  All installed at the same time, for some reason two of the 3 expired or needed replacing as of Dec 2025, while the other is Dec 2027, not sure why they put too old units in my place.  I don't have time to wait on hold, so I am hoping somebody can help me out on how to get two new replacements.  Can I just go to a Telus store and buy some, or do I have to get a tech to come out and do it.

Thanks