"In the olden times"... POTS service in most places wasn't just used for serious/bad events. Perhaps in 3rd world environments. The OP was making a present for

"In the olden times"... POTS service in most places wasn't just used for serious/bad events. Perhaps in 3rd world environments. The OP was making a present for their grandmother's 80th birthday, in 2021, so their grandmother was born in 1940 or later. Someone in their 80s these days is unlikely to be so cognitively impaired as to be worried by phone calls. They're more likely to be facetiming with grandchildren from their iPads/iPhones. In Australia, POTS service was universal and the call costs for local calls was untimed and minimal (perhaps $0.10/call). Timed calls were for longer distances in Australia (STD) or for international (IDD). Unless you're talking about up until the very early 80s, when long distance / international calls required operators.