Retention offer changed after I said I was leaving

Bit fed up tbh. I rang up yesterday because my broadband is going up again and I said I might cancel. The chap on the phone said he could do a loyalty discount and bring it down to £29.99. He took me through a few questions, said it was all sorted, then I got an email this morning and it’s still showing the full price. Has anyone had this before? I’ve been with Nexora years and I don’t want to spend another hour on hold if they’re just going to fob me off.