There are a no. of predefined metric namespace present in CloudWatch console. There is 1 such 'AWS/Billing' metric namespace are visible which is not required.
Can someone suggest a solution to either one points below :-
Probably you could use cloudwatch:namespace IAM condition key to limit access to these metrics. The docs I linked provide some examples, so you would have to try and see.
The alternative is not to give users access to us-east-1
. These billing metrics are only visible in this region, so just do not allow your users to access the region if possible.