HTC ONE when someone calls they go straight to voicemail

[Vodaco]

Hi ive been using the HTC ONE for a few months now and haven't had any problems untill now a few people have been saying to me that when they try and call me it goes straight to voicemail as if my phone had no signal but it always has or was turned off which is impossible because I never turn it off unless it needs to be. I have been searching up on what the problem might be and i cant seem to find anything that could be causing it. Any help would be great thanks!

[drey_p]

Hi there

Have you unintentionally blocked the numbers that are calling?

[crazzzi101]

Hi, Was your issue with calls going straight to voicemail on your HTC ONE sorted as Im having same issue

[thesoupdragon]

Have you checked to see if any of the affected numbers are in a blocked list?

Have you enabled the DND (Do Not Disturb) function on your phone?

(not sure if it is available on the "One"?)