finding user on aws cognito throws error cognitoidentityserviceprovider is not defined - amazon-web-services

Question

I am new to AWS services and I am trying out various services provided by AWS. I have this lambda function on which I am trying to find a user with the phone number on AWS Cognito -
const AWS = require('aws-sdk');
async function findCognitoUser(userId) {
console.log('CognitoUser-FindCognitoUser');
var params = {
UserPoolId: 'poolId',
AttributesToGet: [
'phone_number','displayName'
],
Filter: `phone_number = \"${userId}\"`,
};
cognitoidentityserviceprovider.listUsers(params, function(err, data) {
if (err) {
return 'ERROR OCCURED';
}
else {
return data.Users[0].displayName;
}
});
}
module.exports = findCognitoUser;
I do get an error saying cognitoidentityserviceprovider is not defined
Here is the error on CloudWatch -
"errorType": "ReferenceError",
"errorMessage": "cognitoidentityserviceprovider is not defined",
"stack": [
"ReferenceError: cognitoidentityserviceprovider is not defined",
" at findCognitoUser (/var/task/user-queries/findCognitoUser.js:13:5)",
" at Runtime.exports.handler (/var/task/index.js:14:19)",
" at Runtime.handleOnce (/var/runtime/Runtime.js:66:25)"
]
CODE UPDATED -
const AWS = require('aws-sdk');
async function findCognitoUser(userId) {
console.log(userId);
var csp = new AWS.CognitoIdentityServiceProvider({apiVersion: '2016-04-18'});
var params = {
UserPoolId: 'poolid',
AttributesToGet: [
'phone_number','given_name'
],
Filter: `phone_number = \"${userId}\"`,
};
csp.listUsers(params, function(err, data) {
console.log(data);
if (err) {
return 'ERROR OCCURED';
}
else {
return data.Users[0].given_name;
}
});
}
module.exports = findCognitoUser;