If you find that you and a friend have frequent communication problems, don't accuse them of doing anything wrong. The problem may be on your end. What's more, different sets of friends communicate differently, so what works for one friend may not work for another.
Instead, ask your friend for ideas on how you two can communicate more effectively. Say something like:
"I notice we've had a couple misunderstandings lately when it comes to meeting up after work. How can we fix this? Do you want me to call you before I leave? Send you an email?"
"I wrote on your Facebook wall about the party, but I guess you didn't see it. I use Facebook a lot myself, but if you don't that's okay. Let me know what's the best way to contact you so I don't leave you out next time."
"I know you've been sending me texts during the day, but I really can't get to them. Can you call me instead? I can talk to you more easily that way.