That old flip phone is dual-band GSM-only. In much of the NY/NJ area T-Mobile has severely depreciated 2G service down to a couple of channels running in the LTE guard bands in band 2. You might have a theoretical connectivity but not at all reliable. That phone doesn't owe you anything. Time for a replacement. No other carrier in the US supports 2G GSM any more. It's hit a dead end.