Switch (case) Statement twice in the main loop

can i use 2 Switch (case) Statement’s in the main loop?
if so how?
as i am trying it and its just waiting for the first one to be activated

the first one from the fona library

  char command = Serial.read();
  Serial.println(command);
  
  switch (command) {

    
    case 'a': {
      // read the ADC
      uint16_t adc;
      if (! fona.getADCVoltage(&adc)) {
        Serial.println(F("Failed to read ADC"));
      } else {
        Serial.print(F("ADC = ")); Serial.print(adc); Serial.println(F(" mV"));
      }
      break;
    }}

then the next one looking at what screen is loaded on the touch screen

 // Wait for a touch 
  if (! ctp.touched()) {
    return;
  }

  // Retrieve a point  
  TS_Point p = ctp.getPoint();
  

  int a = page;
     switch (a) {
  
     // --------------check to see if screen 1 is loaded-----------------
     
  case 1: {  // Screen 1 Active As when screen 1 loads it chages the value of page to 1
  
  if ((p.x > 175 && p.x < 201)&& (p.y > 280 && p.y < 320))
  setuser();

You can use as many switch/case you need, nested or in sequence. There is no limitation.
They achieve the same functionality as if/then/elseif/then/... structures.