Create

//  Create a Map to store all the data of a Contact
Map<String, Object> contactMap = new Map<String, Object>(); 
    contactMap.put('Name', 'Breadwinner Inc');
    contactMap.put('FirstName', 'Jack');
    contactMap.put('LastName', 'Rogers');
    contactMap.put('EmailAddress', 'jrogers@burlington.com');

    List<Object> phonesList = new List<Object>();
    Map<String, Object> DefaultPhone = new Map<String, Object>();
    DefaultPhone.put('PhoneType', 'DEFAULT');
    DefaultPhone.put('PhoneNumber', '9988543562');
    phonesList.add(DefaultPhone);
    contactMap.put('Phones', phonesList);

    List<Object> addressList = new List<Object>();
    Map<String, Object> shippingAddressMap = new Map<String, Object>();
        shippingAddressMap.put('AddressType', 'STREET');
        shippingAddressMap.put('Country', 'India');
        shippingAddressMap.put('AddressLine3', 'Kodad');
        shippingAddressMap.put('AddressLine2', 'First Lane');
        shippingAddressMap.put('AddressLine1', '1-24');
        shippingAddressMap.put('PostalCode', '508238');
        shippingAddressMap.put('City', 'Suryapet');
        shippingAddressMap.put('Region', 'India');
        shippingAddressMap.put('AttentionTo', 'User');
        addressList.add(shippingAddressMap);
        
    Map<String, Object> billingAddrFieldMap = new Map<String, Object>();
        billingAddrFieldMap.put('AddressType', 'POBOX');
        billingAddrFieldMap.put('Country', 'India');
        billingAddrFieldMap.put('AddressLine3', '');
        billingAddrFieldMap.put('AddressLine2', 'Srinagar Colony');
        billingAddrFieldMap.put('AddressLine1', '1/78-24');
        billingAddrFieldMap.put('PostalCode', '500008');
        billingAddrFieldMap.put('City', 'Hyderabad');
        billingAddrFieldMap.put('Region', 'India');
        billingAddrFieldMap.put('AttentionTo', 'User');
        addressList.add(billingAddrFieldMap);
        
    contactMap.put('Addresses', addressList);

//  Initializing the RequestJSON Data to be passed.
Map<String, Object> requestJSONMap = new Map<String, Object>();
    requestJSONMap.put('contacts', new List<Object>{contactMap});
    String reqJSON = JSON.serialize(requestJSONMap);

Map<String, Object> reqObj = new Map<String, Object>();
    reqObj.put('version', '1.0');
    reqObj.put('action', 'createContact');
    reqObj.put('requestJSON', reqJSON);
    //Required, if Xero Multi-Org is enabled in Breadwinner. 
    reqObj.put('xeroOrgId', '!aa00TM'); 

//  Placing a request to Breadwinner Global API
Map<String, Object> respMap = bread_winner.BreadwinnerXeroAPI.call(reqObj);
System.debug(respMap);