Understand the idea
Images, downloads and background apps can consume a data allowance unexpectedly. Knowing where data goes helps avoid unnecessary charges.
Put it into practice
Review per-app data usage, set available usage alerts and postpone large downloads until a trusted unmetered connection is available.
Know the limits
A data-saving mode may change image quality or delay background updates.
The wider context
Connection tests are most useful when they are repeatable. Compare similar conditions and record the time of a problem. Faster networking can improve responsiveness, but it cannot create reliable returns or change the rules of an online activity. Avoid tools that require unnecessary device access.
Your next step
Use the practical step above only where it fits your situation. Before an account-specific action, check the current instructions from the service or device provider involved. Write down what you observed and what remains uncertain; that makes a follow-up question more useful.