Nedbank home insurance a ****

We have home insurance on our home. We have constantly a blocked pipe in our home, and the sewerage pipes gets blocked up. According to our policy this is covered. Wording in the policy as follows

Damage to or cracking of swimming pools, tennis courts, patios, paving, terraces, driveways, paths, septic tanks, dams, watercourses, boundary or retaining walls, sewerage pipes and/ or drains, gates or fences. • Any costs for work necessary to prevent further destruction or damage such as piling or underpinning. • Damage to solid floor slabs or any other part of the insured property resulting from the movement of these slabs, unless the foundations supporting the external walls of the buildings are damaged by the same cause at the same time

Yet, when I called them, they just said it is not covered. Now I do not understand. We are paying, and the policy says it is covered, yet the call centre denies this! Is paying Nedbank another ****, and they are taking money each month, and increasing it,? It seems that way to me however. This is structural damage, and not cause by me. This should be repaired by the insurance as stated in the policy. This is not acceptable. policy number P***