Changing tense from present perfect to simple past without time reference

A feature of the present perfect is that it's connected to now. Very broadly it's usage could be broken down into 3 kinds of actions

1) a continuous action reaching into the present often used with 'since' or 'for' (I've been here for hours -- I'm still here now)
2) an action which has consequences in the present (I've lost my key -- I don't have it now)
3) life experiences (I've been to China -- at some indefinite time before now in my life).

It's very common for newpaper articles to start off with a present perfect tense to introduce an event that has happened recently at some indefinite time before now and has consequences in the present (2).

But once the narrative sets in, it is implicit, even without an obvious time marker, that the events are completed events in the past, so there is a switch to simple past. Here are 3 examples of this switch from today's Guardian:

1 The Minnesota congresswoman Ilhan Omar has called the Fox News presenter Tucker Carlson a “racist fool” after he made a racially loaded attack on her live on air.

Carlson, a controversial conservative host and Donald Trump supporter, criticized Omar in a three-minute monologue full of anti-immigrant rhetoric and personal attacks on Omar and her family.

2 Ursula von der Leyen, the nominee to lead the European commission, has signalled she will not reopen Brexit talks with the next British prime minister and stressed the “precious” Irish backstop must be defended.

She said she still hoped the UK would remain in the European Union, while indicating she had no intention to renegotiate the withdrawal deal agreed by Theresa May and EU leaders.

3 The head of the civil service in Northern Ireland has warned against complacency over political limbo as an official report predicts that 40,000 jobs are at risk in the region in the event of a no-deal Brexit.

David Sterling was accused of engaging in “operation fear” in March by a Brexiter Conservative MP after warning of the “grave” consequences for the region.

It is similar to what happens in your text. Personally I think the first 'has said' belongs to the narrative and should also be the simple past, so the whole article should be:

GEFCO Turkey has launched regular freight services from Turkey to Morocco and Tunisia, aiming to offer fast and cost-effective logistics solutions for sea and air transportation. GEFCO Turkey Sales and Marketing Director Serkan Çelik said that the Turkey-Morocco-Tunisia line will enhance the commercial relations between Turkey and North Africa, especially in industries such as textile and fashion. He added that thanks to its long-standing experience, GEFCO Turkey provides value-added services and innovative and digital solutions to its customers. In conclusion, he stated that the logistics provider implements environmentally friendly solutions and sustainability practices such as reusable packaging.