My husband is in Afghanistan and may have more computer access than phone access. First, how do I stay signed in all the time on my iPhone? And second, if he calls me from a computer in Afghanistan to my phone which is in the US, do I need to have credits of any kinds? Will either of us get charged at all?
I can't answer the question about staying signed in all the time. Hopefully someone will be provide an answer. But I can tell you that if your husband calls you Skype-to-Skype there is no charge for the call.
If you do a video call and you're on cellular data, just be careful of not going over your data plan. If you're on wifi....no problem.