YOU SAID:

The only thing I can say is how many people are on the phone

INTO JAPANESE

私が言えるのは、電話に乗っている人の人数だけです。

BACK INTO ENGLISH

I can only say the number of people on the phone.

INTO JAPANESE

電話の人数だけしか言えません。

BACK INTO ENGLISH

I can only say the number of people on the phone.