Reverse charge mechanism and input tax credit

Can any one have answer for my below mentioned  two doubts

 Can I adjust Input credit of serivises for paying my reverse charge laiblility 

eg: I have Rs 700 input credit for paying Rs 5000 agaist my phone bill and same way Iam liable to pay Rs 1000 agaist my secirity expense under reverse chrge mechanism, Can I pay as Rs 300 after taking credit input credit of Rs 700

and can I get credit of Rs 1000 (Full reverse tax amount) in next month serive tax calculation even I adjusted previous month reverse charge agaist input credit of previous month.