英语：如果可能，麻烦给我一个电话好吗？因为我一下打电话找不到你

这个意思，外国人一般说：
please call me when you'er convinient, for i could not contact you.

If possible,can you pls call me ?Because I call you just now but cannot get you .

Sorry you weren't in when i called,please give me a call as soon as possible.

再了些改动,希望不会太生硬

would you mind to give me a call if avalible because i did not reach you.

It's kind of you to give me a call if possible.Because I'm afraid I can't catch you when I call .