insurance refuses to pay claim

i joined clientele because on their adds the say they are hassle free and fast to pay.. also my mother has a policy with them and has never had issues before.. i had a problem with clientele when they refused to pay my claim for hospitalization because they claimed bronchopnemonia to be a pre existing condition.. my so had asthma and has not been treated for any infection over the past year before the current claim... these insurances promise you one thing and do the other when its time to pay up... i want clientele to pay my claim and stop hiding under their claws full of holes...