Phone/Mobicart Paris for 1 week
 

Looking where in Paris, as close to 7th Arrondissement as possible, to buy a mobile phone/SIM package for one week's stay calling locally in Paris only. Is there a better deal if I buy 2 phones to be used by family members for short communication ? What should this cost if I only need to use phone for max 60 minutes total during my stay?
Thanks