Question about web-designer signature

Hi everybody, I’m new here… your forum is amazing. maybe this is the wrong section but I really don’t know where to put my question…

then… I’ve designed a Flash site and after all my work the client doesn’t want my signature and my portfolio link in his site. this makes me angry because people won’t be able to find me. if he doesn’t allow me to put my portolio I will lose future works. and above all I think it’s really a right to put the designer’s name or portfolio under a site. what’s your opinion? it’s like a paint without signature.
for this reason I’ve asked him more money (but still I haven’t tell him how many, and I wish your suggestions about it). he wants to pay me but still asks me to tell him a quote.
have you got similar experiences? what should be my behaviour in this situation? what should I ask him? how this should cost to the client?
please, respond as soon as possible

thank you