Užsakomosios paslaugos = outsourcing,
[ see:
http://baitas.lzuu.lt/~mazylis/julram/7/16.pdf ]
it means the call centre is provided as a service for the needs of a different company (the customer).
thus: "call centre outsourcing services",
http://www.topbits.com/call-center-outsourcing.htmlBut you probably should/would stick to NACE/EVRK anyway, even if it is worded in quite non-native English.
At least add "outsourcing"/"outsourced", otherwise it may convey the wrong idea that it's a company's internal call centre.