I think you should go the replace function.
So, if the string is always in that format, then you can use:
Replace([Text],"Please take note of your order reference:","")
If the text is not always that standard, then you should rather use a regular expressions. To do that, you need to use an object, that will invoke a regex code.
In the standard blueprism objects, you can find:
Object: Utility - Strings C# Action: Extract Regex Values
this is code to implement the regex code.
Dim R as New Regex(Regex_Pattern, RegexOptions.SingleLine) Dim M as Match = R.Match(Text) replacement_result = R.Replace(Text,Regex_Pattern,replacement_string)