How can a reciever verify that transaction data was not altered by 3rd party? My scenario:

My web server:
- Generates private and public, and a wallet address from the public key for a user website account
- Server can not connect to the outside (Can not connect to the Bitcoin network)
- Has a page that allows anyone to send money to the user account wallet address

What I need to do:
- The server needs to know when bitcoins were sent to the wallet address, and how many total bitcoins are at the wallet address

Because web server can not access outside internet, I am using Javascript on the browser side to get the wallet address info by getting https://api.blockcypher.com/v1/btc/test3/addrs/miedePxMt4SDQHjWJyfhbCWvXcm33vzDa1/full and/or https://api.blockcypher.com/v1/btc/test3/txs/681b16b4de3676a5865a85e0bba3097afcc195d928f3167e4d5591c388c1e474?includeHex=true  ... and sending that data to my webserver using a Ajax call to check for the received bitcoins.

Note: I have sent testnet bitcoins to that wallet.

Everything works except 1 problem: The browser user can easily change the bitcoin amounts and trick the web server into thinking more bitcoin were sent.

My question is: What methods can I use on the webserver to verify that the transaction data was not changed by the browser user. The web server has the pub/priv key of the receiving wallet. The webserver has the "bx" libbitcoin-explorer program available and I could potentially install other software.

Can I use the cammands in this diagram at all? https://github.com/libbitcoin/libbitcoin-explorer/wiki/Transaction-Commands
All sensitive operations must be performed on your side. You cannot perform them on the client side and trust the client to pass you the correct information. If you need to call some API to get wallet information, your server needs to make that call.