Android, how transfer big amount of data to web service via ksoap2?

Question

I have a big problem when I try to send big amount of data to web service. I need to send about 20-30 photos to web service. I convert all photo to base64 strings and send to web service. The problem is that when I send 1 photo is ok, but when I try to send 2 photo or more I have out of memory exception. My code:

    public boolean TransferAccidentFromGisToRarParameters(List<String> photos) {
    String METHOD_NAME = "TransferAccidentFromGisToRarParameters";
    String SOAP_ACTION = NAMESPACE + METHOD_NAME;
    request = new SoapObject(NAMESPACE, METHOD_NAME);
    envelope.setOutputSoapObject(request);

    SoapObject arr = new SoapObject(NAMESPACE, "accidentPhotos");

    for (String string : photos) {
        arr.addProperty("string", string);
    }
    request.addSoapObject(arr);
    try {
        androidHttpTransport.call(SOAP_ACTION, envelope);
        SoapPrimitive response = (SoapPrimitive) envelope.getResponse();
        return Boolean.parseBoolean(response.toString());
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
}

Where: photos - a list of base64 strings My web service code block(asmx web service):

        [WebMethod]
    public bool TransferAccidentFromGisToRarParameters(string[] accidentPhotos)
    {
        try
        {
            foreach (var photo in accidentPhotos)
            {
                var item = Convert.FromBase64String(photo);
                var accidentMedia = new AccidentMedia { Content = item };
                entities.media_accidents.AddObject(accidentMedia);
            }
            entities.SaveChanges();
            return true;
        }
        catch (Exception exc)
        {
            return false;
        }
    }

This is exceptions in Android log:

I'll be glad for your answers. Best regards!