My dear, never ever give out your personal information to a stranger unless you know him or he's verified. Thats the basic rules of the internet - this is something to consider even when you want future spells cast for you. This spell caster doesn't seem professional or mature enough to cast spells in the first place - but he could do you harm since he has your personal information.
Write him and say :
1.) you are not going to be using his services,
2.) you are not paying for his services since you don't require it,
3.) it is bad karma to ask for money for service not rendered,
4.) and lastly, you have the help of a powerful coven who can and will do curse reversal should he choose to do one on you.
Contact your coven asap, and inform them of a possible curse spell being cast on you. Get help, from your team and be open to receiving help.
God bless and be safe always,