Which metro station offers Shanghai Public Transportation Card?

You can return the card and get your balance and refund in many service centers. Here is the major ones I know for your reference:
Hongqiao Airport center: the Customer Service Center, B1 Floor, T2, SHA;
Maglev Ticket Window in PVG, at no. 2100, Longyang Road, Pudong New Area;
the main railway station service center, at the exit 5 of the rail station metro station.

You can also return it on your own at the Automatic Tickeing Machine in some metro stations, such as Longyang Road and East Nanjing Road stations of line 2, South Shaanxi Road and Xujiahui stations of line 1 and Zhaojiabang Road and Lujiabang Road stations of line 9.