Phone rings three times then goes to voicemail. Why?

For the past few weeks now every time I try calling my boyfriend from my cellphone to his it rings three times then goes to voicemail. At first I thought he might be ignoring me but that didn’t make sense because we haven’t argued or anything for that to happen. I asked him about it and he said his phone doesn’t show any missed calls from me. We’re in a long distance relationship at the moment and he’s staying with some friends and according to him the network reception there is really poor, so every time I need to talk to him and that happens, I send him a text and he calls me. I don’t really know what to think because, from what I understand, when there’s no network a phone either goes straight to voicemail or you get a message saying the person is out of their coverage area or something else along those lines… I have some suspicions that he might’ve blocked my number on his phone, but that just might be paranoia setting in because he has no reason to do that, and I’m assuming that if he had in fact blocked my number the phone wouldn’t ring at all and he wouldn’t be able to receive my texts… Has anyone here ever had any experiences with something like this before?

Thanks in advance!!