This method retrieves a collection transaction (payment) performed by the customer. For payload explanations for both request and response, click here 
using OneKhusa.SDK; 
using OneKhusa.SDK.Models.Transactions.Collections; 

//code omitted for brevity 

OneKhusaResponse<GetPaymentResponse> response = await client 
    .Transactions 
    .Collections 
    .GetPaymentAsync(new GetPaymentRequest 
    { 
        MerchantAccountNumber = 12345678, 
        TransactionReferenceNumber = "260219DXQ5FB" 
    }); 

if (response is { IsSuccess: true, Data: not null }) 
{ 
    Console.WriteLine($""" 
        SourceAccountNumber: {response.Data.SourceAccountNumber}; 
        SourceCustomerName: {response.Data.SourceCustomerName}; 
        SourceReferenceNumber: {response.Data.SourceReferenceNumber};  
        SourceCurrencyCode: {response.Data.SourceCurrencyCode};  
        BeneficiaryAccountNumber: {response.Data.BeneficiaryAccountNumber};  
        BeneficiaryName: {response.Data.BeneficiaryName};  
        BeneficiaryCurrencyCode: {response.Data.BeneficiaryCurrencyCode};  
        ConnectorName: {response.Data.ConnectorName};  
        AmountSent: {response.Data.AmountSent};  
        AmountReceived: {response.Data.AmountReceived};  
        TransactionFee: {response.Data.TransactionFee};  
        TransactionDescription: {response.Data.TransactionDescription};  
        TransactionDate: {response.Data.TransactionDate};  
        TransactionReferenceNumber: {response.Data.TransactionReferenceNumber};  
        TransactionStatusCode: {response.Data.TransactionStatusCode};  
        TransactionStatusName: {response.Data.TransactionStatusName};  
        TransactionTypeName: {response.Data.TransactionTypeName};  
        DateCreated: {response.Data.DateCreated} 
    """); 
    return; 
} 
//it means an error has occurred: RFC7807 compliant error object
Console.WriteLine($"""
        Type: {response.Error?.Type};
        Title: {response.Error?.Title};
        Detail: {response.Error?.Detail};
        ErrorCode: {response.Error?.ErrorCode};
        Status: {response.Error?.Status};
        Instance: {response.Error?.Instance};
        Errors: {string.Join(";", response.Error?.Errors ?? [])}
""");
Console.ReadLine();