they're literally high-power radio waves.... people have driven through much higher power radio waves with at&t's "long lines" microwave transmitters, and still do today because stock traders use microwave uplinks. microwaves are just higher power radio waves.
everyone hear's "microwave" and thinks about the type of oven, but that only heats water&fat because they have a resonant frequency that the ovens stimulate. when they get old they get detuned and they literally can't heat water at all. if phones used the same frequencies, whenever it rained, or was foggy, or even cloudy, you would get no signal whatsoever.
finally, microwave ovens are rated at things like 700W or 1200W for a reason, that's their output power. (their input is normally higher. older microwaves are between 40-60% efficient, so a 1000W model would draw up to 2.5kW.)
the capacity of phone batteries is nowadays around 2000-3000mAh. 10-15 years ago, it was more like 600-1000, and the strength of cell signals hasn't changed, the extra power is for all the extra smartphone functionalities. so, rememberingphones like old nokias, let's assume 800mAh is equal to a week of standby time, and up to about 6 hours of talk time. phones use 3.6VDC, or 2.88Wh for the duration.
2.88Wh means the phone could do a 2.88-watt activity for an hour, a 5.76-watt activity for 30 minutes, etc.
my particular microwave oven, which is extremely efficient, gets 800W output power from 1000W on 240VAC.
since current can be determined by watts divided by volts, we can discover the microwave oven uses 4 amps. "amp hours" (Ah) are a measurement of stored current, and an amp hour is how much power is used by an amp, in an hour. a cell phone can do at least 6 hours of talk time on about 800mAh, thousandths of amp hours, or 0.8 amp-hours. 0.8 divided by 6 is 0.133, for 0.133Ah-per-hour of talk time. (these calculations are all done with A instead of mA, just because that's the convention and helps to avoid error caused by getting the decimal place in the wrong place, etc)
so, microwave oven uses 1000W, and usually runs for about 5 minutes. 5 minutes is one-twelfth of an hour. this equates to about 83 watt-hours. the phone battery would be able to power the microwave for about 8.6 seconds.
the same battery would let you have a conversation for 6 or more hours. provide a week between charges. and in fact, modern low-power technology etc can run such a "dumbphone" for a whole month between charges on the same size of battery.
this is the kind of huge order-of-magnitude difference between the transmitter in your phone, and the magnetron in your microwave oven.
plus, if you're listening to music on your phone you're wearing headphones and your phone's in your pocket, which is what people recommend if you want to avoid putting it next to your head anyway, making this all completely moot anyway.
but, regardless, cell transmissions from your phone run between 0.6 watts and 3 watts, depending on the distance to the tower (less bars = higher battery use). old fashioned radio signals blast across the country at 5, 10, sometimes 100 or more kW! that's tens of thousands of watts! compared to 3! but you don't think listening to the radio gives you cancer, right?
and, lastly, wifi is much lower power than cell signals, and bluetooth even lower. a smartphone that needs charged daily can become charging once every 7-10 days if the network provides "wifi calling", because then the signal only needs to travel a few tens to hundreds (sometimes thousands, depending on the router's power) of feet within your house, rather than sometimes a few miles away. and bluetooth can only go between about 90 and 300 feet. considerably lower power. we're talking milliwatts.
you'll be fine, they're fine, everything is fine.