Why did my Straighttalk phone give message to do with no roaming available?

[AC Question]

When I was 4 blocks from my house and tried to call home, I got a message telling me something about roaming and the call wouldn't go through. But when I got home, the phone worked and the message my husband had sent me over an hour ago popped up. When I called about it, Straighttalk told me something about a zip code??? I have had straighttalk for a while - never had this issue before. It is a new phone; however.

 

[B. Diddy]

Welcome to Android Central! It may have been a network issue -- how's the coverage in your area? Are you on the edge of a covered area?