The word translated “angel” in the Bible simply means “messenger”. In the Old Testament, the Hebrew word is malak. Sometimes the word is used of a human being. For example, in 1 Kings 19:2, Queen Jezebel sent a messenger (malak) to Elijah. But often it refers to one of God’s heavenly messengers — his angels.
Any of God’s prophets could be called “God’s messenger” since that is what a prophet was. In Hebrew, that would be the same as saying “God’s angel”. Two prophets who are specifically called that are Haggai (Haggai 1:13) and Malachi (who name means “my messenger”).