If the bands on that transmission are adjustable, that should be done. This will keep the car roadworthy with any luck, for a few more years, but it is not a permanent fix. That's what they should have done when they flushed the transmission. Flushing is expensive and isn't all that much work. Some transmissions have the band adjustment inside the sump of the transmission and some have the adjustment on the outside. Flushing does nothing to help is the trasmission isn't clogged with crud. Eventually this transmission will completely fail and need rebuilding or replacement with a used good transmission.