No Service ATT Wireless coverage at my office in Carifornia

ATT does not have service at my office in Carifornia. All other providers Verizon, Sprint all have excellent signal. Called ATT multiple times, each time they do trouble shooting, advise a microcell. But 100+ users are impacted at this location. 

ATT says walk away if you like to pay me money to cancel the contract. But what about the services I am eligible for and not getting. Everyday 8 hours I am without service. 

You call ATT sales they say they have 99% coverage all is a hoax.