That will depend on your mast. Vodafone round me uses 800MHz, 2100Mhz and 2600Mhz for 4G. Generally I'm connected to either 800MHz or 2100Mhz
An app like NetMonster will display and keep a log of your connections. Network Cell Info is another one.
Remember Cell frequencies are liable to change over time as networks change things for 5G and enhanced 4G with the closure next year of 3G on Vodafone and EE.
What handset do you have as WiFi Calling would be a free and permanent solution.
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