Solution

The puzzle follows the rules of Rotary Phone. The numbers received from this are: 746, 487, 348, 364, 348, 384, 733, 646, 334, 448, 847, 333, 687, 749, 896. These numbers can be translated to letters using the Multi-tap Phone Cipher. The dots represent how many times to tap a number.

This says: RING UP FIVE OH FIVE THREE NINE EIGHT THREE FOUR SIX TWO. The phone number isn't up anymore, but puzzlers who called received this audio:

The recording gives ten words which are different pictures from The iPhone which also correspond to digits.

Word	Corresponding Number	Solution Letter
Composer x1	4	G
Football Team x3	7	R
Computer	2	A
Band x3	8	V
Composer x3	4	I
Band	8	T
Roast Dinner x3	9	Y
Band	8	T
Composer x3	4	I
Porsche x2	3	E

Using the same method to decode the numbers (the echoes tell how many times to tap the number) provides the solution.

GRAVITY TIE

This was inspired by Phone Lines from the 2019 Galactic Puzzle Hunt. Thanks to the author of this puzzle, Lennart Jansson (Discord: zhanrnl#8589), for helping me figure out how to get a phone number for the puzzle.