Calling WCF Service using jQuery in ASP.Net

Dear Sir

How can I  call wcf service from jquery and also I dont want to change wcf functions as those functions are also used from some where else from other platforms..

I know how to retrive in json format but for this i will have to change in wcf functions i dont want to do that...

please help...

<OperationContract()>
        Function GetBedTypeList(ByRef strErrMsg As System.Collections.Generic.List(Of String), _
                                                    ByRef chrErrFlg As Char, _
                                                    ByVal pcompanycode As String,
                                                    ByVal pdiv As Integer, _
                                                    ByVal ploc As Integer) As System.Collections.Generic.List(Of CWReadClasses.clsBedTypeMaster)