How can sort alphabetically of users using Meteor?

I am using meteor user accounts package. I want to sort all users according to alphabetically ascending order. My Collection Structure is like this

{
    "_id" : "6J3jjZB7DMRyPcTxh",
    "createdAt" : ISODate("2018-05-28T13:07:03.428Z"),
    "services" : {
        "password" : {
            "bcrypt" : "$2b$10$1W2g1Ceal39uUz0JVZ1JSuT1M9gKfKas.5VZ8ThH2Ga6cPp7SY6zO"
        },
        "resume" : {
            "loginTokens" : []
        }
    },
    "emails" : [ 
        {
            "address" : "vishnu@gmail.com",
            "verified" : false
        }
    ],
    "profile" : {
        "username" : "vishnu singh",
        "regPhone" : "8088***0297",
        "discount" : "66.66",
        "isDeleted" : false,
        "role" : "user"
    }
} 

Query is :

    responseArray = Meteor.users.find({ 'profile.isDeleted': { $ne: true }, 'profile.role': { $ne: 'admin' } }, { sort: { 'profile.username': 1 }, skip: skip, limit: limit }).fetch();

My skip is 0 and limit is 25. Skip limit change the second time to skip 25 and limit 25. How can sort all users according to the username? please help.

The issue is with case sensitive. I think MongoDB doesn't support find and sort with case sensitive. I used aggregation and finally get the solution.

  responseArray = Meteor.users.aggregate([{
                    $match: {
                        'profile.isDeleted': { $ne: true },
                        'profile.role': { $ne: 'admin' }
                    }
                },
                {
                    "$project": {
                        profile: 1,
                        emails: 1,
                        "insensitive": { "$toLower": "$profile.username" }
                    }
                },
                { "$sort": { "insensitive": 1 } },
                { "$skip": skip },
                { "$limit": limit }
            ])