I would like to ask people living in Russia: I have a Russian friend. I sent him a message on my mobile phone in China (M-Zone), and he could receive it, but

There must be that plus sign before your mobile phone number +86.

Or after you send it to him, let him read the message and reply directly.

Sometimes you get confused or blank messages.

Then you can only send pinyin

Or maybe he doesn't have enough money in his card. . . .