Do you have a boy? Boys tend to be a bit "lazier" in terms of talking.
What you described I wouldn't think there is any reason to panic and think immediatly about autism. Don't let yourself drive crazy.
Trust your child and give him/her enough attention, love and let him/her play a lot.
Around this age they don't necesserly play with other kids, but they like to be around them. '
My son was reluctant to speak, my friend's son already spoke 2 languages at that time(they're same age). It was sometimes frustrating for me, and I had to reassure myself that he is different and each of them have their own time to do things.
Not responding to a call, well I could complain about that too. There are times, when I have to call 5 or more times.
I know you meet other moms, who's kids do respond right away. One way of interpreting is that he/she's a very intelligent person and want to do things on his/her way. It's definitely harder on you, but I'm sure we are talking about a smart kid.
Good luck to you, have patience and trust your little one.