After really great service, now disappointed and out the door

I am an exisiting and loyal client on Dotsure . My pet developed a condition and I wanted to upgrade her cover to be able cover treatment which is only oral and fairly inexpensive. I was told they would not cover it because it is a pre-existing condition (even though I am with them, just on a lower plan) and I said that I would be happy to wait an exclusion period - they refused flat out. I really liked the level of service that I received while with them, but this instance shows me that they only care to a certain point. Other pet insurances were willing to cover her, despite me not being a member. I am very disappointed in Dotsure