Unilateral amendment of the contract – special right of termination?

Hello people Need a brief assessment of the following facts Have insured my new car with the Direct Line after I had already insured 2 cars there before. One of them also comprehensive. Before my present I had insured a car there for about a 3/4 year without comprehensive insurance. At the service phone I was offered an offer with SF 16 also for the fully comprehensive and that was then documented in the application. Now I received mail today regarding a change of contract from SF 16 to SF 10! That’s almost 70 Euro difference It’s just like that, I mean if no SF16 would have been offered to me there then I might have decided for another insurance. LG Ralf