PIP Light Review

Due to postal delivery delays I received my review form only days before it had to be returned. I decided to tick the 'no change' boxes for each component so I could return it the same day, even though I could argue that my condition had become worse. My worry is that, in view of the ongoing delays of up to 3 weeks in post deliveries in my area, I might miss a face to face appointment or a medical and, therefore, face my award being disallowed. Should I write or telephone the DWP to explain this problem?