Authentication in SOAP header using C# and SOAP UI

I'm currently working on integrating a SOAP service into my C# application and I'm having trouble implementing authentication using SOAP headers. I just want to read the username and password from the SOAP request. I am testing on SoapUI.

Here is the request structure:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:tem="http://tempuri.org/" xmlns:onl="http://schemas.datacontract.org/2004/07/OnlineDataExchange">
   <soapenv:Header>
      <wsse:Security>
         <wsse:UsernameToken>
            <wsse:Username>SOAP_ODE</wsse:Username>
            <wsse:Password>123456</wsse:Password>
         </wsse:UsernameToken>
      </wsse:Security>
   </soapenv:Header>
   <soapenv:Body>
      <tem:SendPin>
         <tem:request>
            <onl:TransactionID>?</onl:TransactionID>
            <onl:MSISDN>?</onl:MSISDN>
         </tem:request>
      </tem:SendPin>
   </soapenv:Body>
</soapenv:Envelope>

This is my code:

SendPinRequest.cs:

using System.Runtime.Serialization;

namespace OnlineDataExchange
{
    [DataContract]
    public class SendPinRequest
    {
        [DataMember(Order = 1, IsRequired = true)]
        public string TransactionID { get; set; }
        [DataMember(Order = 2, IsRequired = true)]
        public string MSISDN { get; set; }
    }
}

IPinService.cs:

using System.ServiceModel;
using System.Threading.Tasks;

namespace OnlineDataExchange.Contracts
{
    [ServiceContract]
    public interface IPinService
    {
        [OperationContract]
        Task<SendPinResponse> SendPin(SendPinRequest request);
    }
}

PinService.cs:

using OnlineDataExchange.Contracts;
using SoapCore;
namespace OnlineDataExchange.Services
{
    public class PinService : IPinService
    {
        private readonly IConfiguration _configuration;

        public PinService(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        public async Task<SendPinResponse> SendPin(SendPinRequest request)
        {
            string resp_code = "00";
            ???? // Here I want to retreive the username and password from the SOAP Header
            if (request == null) throw new ArgumentNullException(nameof(request));
            // Check MSISDN
            if (resp_code == "00") resp_code = ValidationUtils.ValidateMSISDN(request.MSISDN);
            // Check Password
            if (resp_code == "00") resp_code = ValidationUtils.ValidatePassword(password);

            // Check credentials
            Authentication au = new Authentication(_configuration);
            if (resp_code == "00") resp_code = au.AuthenticateUser(username, password);

            return new SendPinResponse
            {
                TransactionID = request.TransactionID,
                ResponseCode = resp_code,
                ResponseText = ResponseCodes.ResponsesDictionary[resp_code],
                MSISDN = request.MSISDN
            };
        }
    }
}

I tried a lot of solutions found on google but none worked and they all seemed outdated...