My cat has really bad fleas so I gave him a bath with cat flea shampoo and applied the flea treatment I got at the pet store to the back of his neck. He still has fleas. The fleas are still crawling around in the treatment like its nothing. Do i have to wait for the treatment to work?

Five days ago, I gave my cat a liquid flea treatment (the kind administered to the back of the neck). Today, while someone was cat-sitting for me, they informed me that they had also given my cat a flea treatment of the same kind. What should I do for my cat? I can’t reach a vet as it is after hours and all offices are closed. I can’t bathe the cat as she is deathly afraid of water and will attack. What can I do?