This is probably a very simple problem to solve, but I am setting up a node.js backend using express for my Dapp and I can now deploy new contracts just fine.

I now need to figure out how to make calls to a function in an existing contract (created previously in Remix). I have the following syntax for setting up the provider. This works, at least for creating a new Insurer:

    const Web3 = require("web3");
    const HDWalletProvider = require("@truffle/hdwallet-provider");
    
    require('dotenv').config();
    const provider = new HDWalletProvider(process.env.MNEMONIC, process.env.INFURA_URL);
    
    var contract    = require("@truffle/contract");
    
    const insurerArtifacts = require('./build/contracts/Insurer.json');
    var myInsurerContract = contract(insurerArtifacts);
    myInsurerContract.setProvider(provider);
    
    const platformArtifacts = require('./build/contracts/Platform.json');
    var myPlatformContract = contract(platformArtifacts);
    myPlatformContract.setProvider(provider);

The function call I make is as follows:

	var insurerAddress = '0x...';
	var myClientUIC = req.body.clientUIC;
	var myClientName = req.body.clientName;
	var myClientGroup = req.body.clientGroup;
	var myClientNACE = req.body.clientNACE;
	var myCreditLine = parseInt(req.body.creditLine);
	var myCreditLineDate = parseInt(req.body.creditLineDate);
	var myClientCurrency = req.body.clientCurrency;
	var myClientCity = req.body.clientCity;
	var myClientCountry = req.body.clientCountry;

	myPlatformContract.at("0x...").methods.createClient(myClientUIC, myClientName, myClientGroup, 
		myClientNACE, insurerAddress, myCreditLine, myCreditLineDate, myClientCurrency, myClientCity, myClientCountry,
		{ from:provider.getAddress() })
        .once('transactionHash', function(hash) {
            console.log("TxHash: " + hash);
        }).on('receipt', function(receipt) { console.log("receipt: " + JSON.stringify(receipt)); })
			.then(function(result) {
        }, function(error) {
            console.log(error);
        });

The error I get is:

    TypeError: Cannot read property 'createClient' of undefined 

   
However, createClient is a function and I have checked that all the parameters have values. Does createClient itself need to be called differently?

I would appreciate any help you an give me with this beginner's issue! Many thanks. Phil