The only reason to answer the phone when a customer calls is to make the customer happy.
If you’re not doing this or you are unable to do this, do not answer the phone. There is no middle ground on this discussion. There are no half measures. Saving 50 cents a call with a complicated phone tree is a false savings. Think of all the money you’ll save if you just stop answering altogether. Think of all the money you’ll make if you just make people happy.