What is described as unlimited?
Identify the eligible activity named in the terms. An unlimited domestic-data allowance does not by itself define calls, roaming, hotspot permissions or speed. A feature for particular apps is narrower still. Read the definition attached to the exact tariff and avoid carrying a headline from one product into a different agreement.
Why might speed still vary?
Local radio conditions, congestion, the handset and any tariff speed level can all affect performance. A larger allowance does not remove those factors. For work, assess upload consistency and latency as well as downloads. If the issue is a weak connection at home, simply buying more data may not address the underlying limitation.
What changes with a hotspot or router?
Check permitted device categories and reasonable-use conditions. Laptop updates and backups can use substantial data without appearing in the phone’s ordinary browsing history. A phone hotspot also brings battery and heat considerations. A dedicated router can behave differently from the phone even when using a related service. Test the task rather than assuming the allowance guarantees suitability.
What changes outside the UK?
Travel may use a separate allocation, a pass or a different fair-use rule. Confirm the destination and length of stay. A domestic application feature need not operate identically abroad. Keep ordinary data, eligible app activity and roaming as separate lines in the comparison so the most attractive headline does not hide the part you actually depend on.
General practical explanation; confirm plan-specific rules with the provider.