Where can I find out the expiry data on my mobile promotional plan?

I couldn’t find any documentation about my mobile promotion plan that was bundled when I purchased my home internet. I’ve already chatted with three different agents, and each gave me a different answer while also urging me to apply the promotion immediately. Honestly, it feels very inconsistent and confusing.

Where can I find the official expiration details for this promotion? Or does it actually have an expiration date at all?