A cheap SIM (card): typically a low-cost SIM card or plan offered by MVNOs; may differ from major carriers in speed or services.
通信費を節約するために格安ＳＩＭに乗り換えた。
I switched to a cheap SIM to save on communication costs.
格安ＳＩＭは月額料金が安い反面、混雑時に速度が落ちることがある。
Cheap SIMs have low monthly fees, but their speeds can drop during peak congestion.
格安ＳＩＭを使うときは、対応周波数やSIMロックの有無を確認しよう。
When using a cheap SIM, check supported frequencies and whether the phone is SIM-locked.