ansagen
to announce
To announce something publicly, for example the next song, the next program item, or the next stop.
Der Schaffner sagte den nächsten Halt an.
The conductor announced the next stop.

to announce
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to announce
To announce something publicly, for example the next song, the next program item, or the next stop.
Der Schaffner sagte den nächsten Halt an.
The conductor announced the next stop.

'Ansagen' is a separable verb. The prefix 'an-' goes at the end in a main clause. In subordinate clauses or after a modal verb, the verb stays together.
Der Moderator sagt den nächsten Gast an.
The host announces the next guest.
You can often recognize which meaning is intended from the object. If you say 'einen Halt' (a stop) or 'ein Lied' (a song) with 'ansagen', it is an announcement. If you say 'den Kampf' (the fight), it is a declaration of war. If you say 'den Sieg' (victory), it is a confident claim.
Im Zug wurde der nächste Bahnhof angesagt.
The next station was announced on the train.
In the meaning 'ankündigen' (to announce), 'ansagen' is often used for public information. Typical phrases are: 'eine Haltestelle ansagen' (to announce a stop), 'das Wetter ansagen' (to announce the weather), 'einen Programmpunkt ansagen' (to announce a program item), or 'ein Lied ansagen' (to announce a song).
Im Radio wurde gerade ein Stau auf der A5 angesagt.
A traffic jam on the A5 was just announced on the radio.
The expression 'jemandem/etwas den Kampf ansagen' (to declare war on someone/something) is fixed. The person or thing you want to fight against is always in the dative.
Die Ärztin hat den Kilos den Kampf angesagt und eine Diät begonnen.
The doctor declared war on the kilos and started a diet.
When 'ansagen' announces an intention or goal, the usage is colloquial. It often expresses great self-confidence or a challenge.
Vor dem Spiel hat der Kapitän den Sieg angesagt.
Before the game, the captain announced victory.
to report / get in touch
'melden' and 'ansagen' both have to do with passing on information. 'melden' is used when you give information to the responsible person or office, often officially or because of a rule. 'ansagen' is used when something is announced publicly, for example on a train, on the radio, or at an event. The confusion arises because in both cases someone says something. The difference is: 'melden' is more directed at a specific office or authority, while 'ansagen' is directed at an audience.

Am Bahnhof sagt eine Stimme die nächste Haltestelle an.
At the station, a voice announces the next stop.
Der Hausmeister meldet den Wasserschaden sofort der Verwaltung.
The caretaker reports the water damage to the administration immediately.