You can use BindingList<KeyValuePair<string, string>>:
var items = new BindingList<KeyValuePair<string, string>>();
items.Add(new KeyValuePair<string, string>("Mpost", "Posted"));
items.Add(new KeyValuePair<string, string>("Call", "Calling"));
items.Add(new KeyValuePair<string, string>("RScan", "Re-Scan"));
myComboBox.DataSource = items;
myComboBox.ValueMember = "Key";
myComboBox.DisplayMember = "Value";
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