iOS调用系统的电话功能

NSString *allString = [NSString stringWithFormat:@"tel:10086"];//注意电话号码不能包含空格，包含空格的电话号码拨打没有反应

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:allString]];

示例：

NSString *num = [[NSString alloc] initWithFormat:@"tel:%@",phone];
num = [num stringByReplacingOccurrencesOfString:@" " withString:@""];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:num]];