Form 12B amendment

I have received wrong form 12B in which my previous concern has deducted IT on HRA though rent receipts are available .Now , they are regretting to provide revised form 12B. Please revert whether

(1) My previous concern can amend form 12B after submission of rent receipts or same is  not possible as per present laws.

(2) If not, then can I submit rent receipts to my current concern.

(3) If not , then can I claim for IT return against those receipts.