The first way to refuse is to hang up the phone directly.
This kind of person usually won't listen to what you say and just hang up.
The second way to refuse is to refuse politely.
For example, he doesn't like it or doesn't need it, and then politely say thank you and hang up.
The third way to refuse is to refuse by teasing.
For example, he won't answer your question directly, but say something else to prevaricate you.
These are common problems encountered on the phone, but I personally advise you not to be discouraged, and you will succeed after several times.