Azure Service bus message deserealization in Logic apps

Question

Hi
I am calling child logic app from parent and passing Sessionid from parent to child.
Child Logic app will listen from Queue with the SessionId it received from the Parent Logic app

it is working fine, But when i am trying to convert the Payload receive from Service bus Queue to string using below expression in compose action

base64ToString(body('Get_messages_from_a_queue_(peek-lock)'))

Error

InvalidTemplate. Unable to process template language expressions in action 'ClaimData' inputs at line '1' and column '2147': 'The template language function 'base64ToString' expects its parameter to be a string. The provided value is of type 'Array'. Please see https://aka.ms/logicexpressions#base64ToString for usage details.'.