Hi.
I really don't have any idea why your mom is saying no.
But why do you want a beeper so badly? If it's because your friends use them to communicate, that is probably not an answer that would win your mother over. Instead, consider telling her about a beeper benefit that she can appreciate: She'll always be able to locate you if you are wearing a beeper and are out with your friends.
In fact, you could consider getting a beeper on a trial basis and making a deal that if you don't respond to one of her pages, you will give it back. Showing responsibility about using a beeper is one way she could warm up to the idea.
If you have done your research and found a plan that makes sense for you (be sure to read the fine print to see if there are any hidden costs, or if you have to keep the beeper for a certain amount of time, for example), it also shows your mother that you know what the plan is all about.
But the key thing here is that you say you are willing to pay for the beeper yourself. Do you have a part-time job, or are you talking about using your savings to pay for a beeper? If you are talking about a savings account that is set aside for something like your school tuition, then you might want to consider getting a job so that you can earn your own money to pay for a beeper.