By their very nature, mobile phones make telephony seem unreliable.
I question the word “seem”. Modern telephony is unreliable.
An excellent essay on why we don’t make phone calls any more, without even mentioning Automatic Voice Response systems. Everything that Prof. Bogost describes here explains why we don’t call our friends so much any more, and AVR on top of all that explains why we hate, hate, hate to have to call any business about anything any more.