REST/SOAP Api to update fixed asset mass additions distribution units

Hi ,

In Fixed Asset Mass Addition I want to update the Units using REST/SOAP API the below Rest API is not allowing me update the same :

fscmRestApi/resources/11.13.18.05/erpintegrations

{    "OperationName": "processTransaction-updateMassAddition",    "ParameterList": "{ P_MASS_ADDITION_ID : 126001,P_PAYABLES_UNITS   :2, P_UNITS: 3}"}

Even if its gets updated then after posting it to FA_ADDITIONS_B tables the current unit still remains the same . So do we have any alternative to achieve the same using any other Rest/Soap Api.