Starting late last night (possibly earlier, but this is when we first noticed), none of our family’s  three Koodo prepaid phones are able to place or receive a call.  When we try to place a call, it disconnects almost immediately and says ‘call failed’ - when someone outside our family tries to call us it seems to start to connect, then just disconnects immediately.   All accounts are confirmed active and have minutes.   Texting and other functions are working fine.  Per a Google search for a solution, we have switched airplane mode on and off, and restarted the phones.