Mail attachment quarantined on iphone
This has nothing to do with your iPhone, or your competence. You received a txt document, in place of the original document, so the original was never sent to you, or rather, it was restricted, by a security tool, from leaving the originators network. 

This is very likely a Data Loss Prevention tool (possibly from Trend Micro) that sits on the originator's network, that is preventing the emailing of this document. These tools 'sniff' the contents of an email and attachment, and if they find strings similar to things like social security numbers, membership numbers, or other sensitive corporate data, they will remove the attachment and not allow it to be sent. They also can be set more generically, like not allowing any Excel document to be sent.

You will need to contact the originator, and explain that a security tool on their network is removing the attachment. They will need to ensure that the attachment meets their company's security standards before the system will allow it to be sent.