When a private company calls you to offer some kind of service, what's the best way to response to the caller when you're not interested in the service? or when someone else from the same company has already called you a few days ago offering the same service?

Hmm ok, it looks like interesting, but at the moment, I'm not interested in that kind of service
?

What if I'm undecided if I want or not the service?

Hmm, it looks like interesting, but for now I prefer to sit back and analyse this offer together with my father, and when we make a decision I'll let you know.

Can you tell me more natural sentences to use in those cases?

Thanks