Firstly, you should have not delayed in approaching them gain on non receipt of the invoice. Further, you had paid the money to them, hence it is their responsibility to contact you and confirm whether you have got your replacement done or not.
You need to serve notice to them asking for the replacement of the Lenovo Tablet or reimburse you the costs to be incured on its repair. If they fail to do so then you have approach the district forum against the company with your grievance.
Adv. Rohit Dalmia