Customer service made a mistake, did not add Black Friday discount

I call last month November to renew my contract and add tv channels in new subscription. on the call kpn employee said you will receive on 7th december a device for tv receiver. i say ok. i wait for a long time no device

i call again she said you have no tv channels . we forget to add this service . i say ok cancel the contract . she said you cant i say ok add the channels which you agreed for black friday discount scheme she said not possible . i say then how? she said you have to pay more 10 euros every month

is this fair? wy i should pay? it was my mistake or from kpn employee

i want to complain to department now

add the channels or cancel the agreement