I have a ZTE WF23CA on the Koodo Home Phone. It mostly works but on some numbers when I tried to enter voicemail option numbers or extension numbers it gets a fast busy signal. Very consistent on the telephone numbers that fail. On numbers that fail some extension numbers work but others fail. I have tested with several different phones connected to the ZTE and all fail on the same numbers. I can call the numbers that fail on my cell phones or other landlines or Viop phones and none of the fail on the bad numbers. Koodo support after several calls over 2 months indicate it is a hardware problem. I have tried different sims and they all fail in the ZTE unit. I took the ZTE in for repair and it came back unchanged. I took it in again and they replaced it with the same model number. The new one fails on the same extension numbers on the same phone numbers. As so many companies rely totally on voicemail systems these days I need to get this fixed. Anyone have any experience or ideas on this problem?? (Also both units also get ‘xbx type errors while dialing numbers intermittently (number cannot be completed as dialed etc). The errors come up before the number has been completely dialed.