Iphone Wi-Fi connects to comcast router but internet doesn't work?

Hi, I'm really desperate here.
The problem: my iphone 4s does connect to my home Wi-Fi network but then the internet doesn't work, even if the Wi-Fi signal is full on.
My router is technicolor TC8305C.
I have already tried:
-reboot router
-reboot iphone
-reset network settings on iphone
-change the channel from automatic to manual ( I tried 1, 6 and 11)
-change the security protocol to WPA2 (AES)
-change the protocol from 802.11 g/n to 802.11 b/g/n
every time I tried something new I did reset the network settings on the phone turned it off and restarted from the beginning, it always sees the network, connects alright but then internet doesn't work.
I'm receiving emails randomly once a day.
The network is fine because on my laptop I connect and everything works perfectly…
Now I've called Comcast and they say the problem is the iphone and that I need to set some configuration, but they'll tell me only if I pay them 79.99 $ (?)
On the apple site there's not an hint on any special iphone configuration for the Wi-Fi… Does anyone knows what these special settings are?
Does anyone knows what else I can try?
I don't want to buy another router…

If you can't find the amswer on the iPhone forums via Google, I suggest you try asking on Apple's site.

For any wireless device to connect to the network, you must match the encryption type (WPA, WPA2, etc), must enter the proper preshare key (wireless password), and if MAC address validation is active on the router, the MAC address of the iPhone network interface must be entered into the router MAC address validation table.

We can't from here determine which is not correctly done but if you follow a logical troubleshooting method you will find it.

I suggest you first check the encryption type and password to make sure it is correctly set on the iPhone. This info can be found on the router wireless configuration section. If this fails to connect go to router wireless security section and investigate MAC address validation and if needed, make sure your iPhone MAC address (Apple calls it the Wi-Fi address), is entered in the validation table.

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