How to make a Minecraft Command Block say multiple things?

In 1.12 you need at least 7 command blocks, possibly 8 if you want to reset it again, first run the following command in chat:

"/scoreboard objectives add ElevatorClicks dummy Elevator button presses"

Then get a command block and place it after the button put the following command into it:

"/scoreboard players add @p ElevatorClicks 1"

Then get a repeating command block either by giving one or by placing one and putting it in repeat mode. Place it near the elevator and put the following command in it:

"/testfor @a[score_ElevatorClicks_min=1,score_ElevatorClicks=1]"

Place a conditional chain command block behind it and place this command in it:

"/say You called the elevator"

Place a normal chain after it with the following command:

"/scoreboard players add @a[score_ElevatorClicks_min=1,score_ElevatorClicks=1] ElevatorClicks 1"

Place another chain with the following command:

"/testfor @a[score_ElevatorClicks_min=3,score_ElevatorClicks=3]"

Place a conditional chain command block behind it with this command:

"/say You already called the elevator"

Place a last chain with this command:

"/scoreboard players set @a[score_ElevatorClicks_min=3,score_ElevatorClicks=3] ElevatorClicks 2"

For a resetting command block place a normal command block that can be triggered either by a button or by some other signal. Paste the following command in it:

"/scoreboard players set @a ElevatorClicks 0"

(ElevatorClicks can be any name so can the things after /say)

(If your in 1.13 look here) In 1.13 it takes 5/6 and you do the following. Run the first command in chat:

"/scoreboard objectives add ElevatorClicks dummy Elevator button presses"

Place a command block after the button and place this command in it:

"/scoreboard players add @p ElevatorClicks 1"

Then get a repeating command block and place it somewhere near the elevator. Put in this command:

"/execute if entity @a[scores={ElevatorClicks=1}] run say You called the elevator"

Then put on a chain with this command:

"/scoreboard players add @a[scores={ElevatorClicks=1}] ElevatorClicks 1"

Put on another chain with this command:

"/execute if entity @a[scores={ElevatorClicks=3}] run say You already called the elevator"

And a last chain with this command:

"/scoreboard players set @a[scores={ElevatorClicks=3}] ElevatorClicks 2"

For a resetting commandblock place a normal one with this command:

"/scoreboard players set @a ElevatorClicks 0"

And make sure you can trigger it.