Sightsavers — sightsavers ngo calls for donation

My wife got a call from someone claiming that he is calling in behalf of sightsavers perambur chennai from number [protected]...
I intervened and i asked him on how did he got the number.. He explained some stories..
And when i asked how much money he wanted he cut the call..
Questions
1. Why an ngo person should call from mobile.
2. Why doesn't he have patience to answer my question, even if he is genuine to make blind people see.. He should not have cut my call.. He did ruin my 15 mins of valuable time.. If he thinks i'm wasting his..

I don't think ngo has got any rights to collect anyone numbers and make any calls to anyone asking them to contribute,, i seriously doubt these people's intentions..
There is no way i could see my contribution actually spend on people with need...