Android : Android -C2call Add credit to user Programetically

Hello all i need to add calling functionality in my app for that i have used c2call SDK

I am able to carete user using

final SCRegistrationData data = new SCRegistrationData();
    data.setFirstName(myDetail.getName());
                    data.setLastName(myDetail.getUserId() + "");
                    data.setPassword("123456");


                    data.setEmail(myDetail.getEmail() + "");
                    Locale.getDefault().getCountry();

                    String str = myDetail.getPhoneCode();

                    data.setCountry(myDetail.getcountry());



                    response = __facade.registerNewUser(data);

                    System.out.println("Response+++" + response);

the above code able to create new user

Now in next step i want to add credit t user

for that i find this public method

public boolean addCredit (int valueInCent, SCCurrency currency, String transactionId, String receipt)

Ads credit the specified recipient.

Returns true, on success. but not able to find what is the String transactionId, String receipt in argument and i am not finding any reference doc to find that

Please help to solve the problem

__facade.addCredit(10, "Euro", arg2, arg3);