Need one BTC Testnet RPC endpoint for testing.

Hello:
I want to use RPC Client to retrieve account balance for one test net account.
I have added some funds using faucet, I can use Bitcoin Core program for Windows 10 to get the account balance, but I want to use RPC client to do the same job.
However, I looked at your repo, I found it is very complicated, I can't find any code sample for my job. I saw there are a number of tests in the repo, but how I can write a simple C# code to find account balance for one test net account?
Using curl, the command looks like this:
curl --location --request POST 'bitcoin_testnet_rpc_url'
--data-raw '{"jsonrpc": "2.0",
"method": "getbalance",
"params": ["Account_Address_BTC_TESTNET", null, null, null],
"id": "1"}'
But I need at least one BTC Testnet RPC endpoint for testing.
Please advise on how can I find one.
Thanks,