This following example is a small snippet of code I found to call a simple web service and return it to a NSURL string. You will need to use a XML parser to parse your web services data. This web service sends the request information in the url.

-(BOOL)CallService:(NSString *)value
    // Call web service to verify a session object or string
    BOOL result = YES;
    // Create the objects for calling the web service
    NSString *buildURL = [NSString stringWithFormat:@"", ID];
    NSURL *url = [NSURL URLWithString:buildURL];
    //Call the request
    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url;
    // Create the objects for parsing the xml data returned by web service
    NSData *data;
    NSURLResponse *response;
    NSError *error;
    // Call the web service
    xmlData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
    [parser setDelegate:self]; // You can create a parser method to remove any whitespaces or apending chars if needed
    reply = [[NSMutableString alloc]init];
    // Read the xml data returned by the web service
    [parser parse];
    if([reply isEqualToString:@"yourErrorResponse"]) //If your service returned ect do this 
        ErrorMessage = @"Error";
        return NO;
    if([reply isEqualToString:@""] || reply == NULL) // Else if no reply do that, or use error object
        //No reply from web service
        ErrorMessage = @"Connection Error";
        return NO;
    return result;	//Else return the result or error
-(NSString)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
    reply = [NSString stringWithString:string];
    return reply;