Sounds like you have a hydraulic leak, and the oil is contaminating the pads. I don't know the shop, but you're right that the mechanic was certainly disinterested. Simply bleeding the brake won't solve the cause, it only treats (temporarily) the symptom. It's equivalent to putting air in a flat tire without patching the leak.
Go back, talk to the manager, and have him assign a new and caring mechanic (if he has one), and have the entire brake and line connection until he finds and addresses the leak. The likeliest cause is a poor line connection at the brake, but it could also be a faulty caliper.
BTW- a leaky caliper can happen to anyone, and yes new brakes sometimes squeal a while before settling in. So far so good, stuff happens. In fact, this was an opportunity for the store to show that they stand behind their products. Instead, when you walked in with a very obviously leaking brake you got blown off as an inconvenience. Unless you sense a very positive attitude from the manager or owner, I wouldn't spend another nickel in that store.
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