Unwillingness of ABSA Home Insurance to assist

As an ABSA client since 1981 I find ABSA Home Insurance's unwillingness to assist me as appalling. On 1 November I discovered that our drain is not flowing. A plumber tried to open it without success and assessed that the drain collapsed UNDER our 100 year old house. I registered a claim on 2 November (***). I know the policy excludes a blocked drain