Это добилось цели.Также мне пришлось удалить куки.
NSDictionary *dictPrivacy = [NSDictionary dictionaryWithObjectsAndKeys:@"EVERYONE",@"value", nil];
SBJSON *jsonWriter = [[SBJSON new] autorelease];
NSString *strPrivacy = [jsonWriter stringWithObject:dictPrivacy];
NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:
message, @"message",
strPrivacy,@"privacy",
nil];